Resource functions for ARM templates

  • Article

Resource Manager provides the following functions for getting resource values in your Azure Resource Manager template (ARM template):

To get values from parameters, variables, or the current deployment, see Deployment value functions.

To get deployment scope values, see Scope functions.

Tip

We recommend Bicep because it offers the same capabilities as ARM templates and the syntax is easier to use. To learn more, see resource functions.

extensionResourceId

extensionResourceId(baseResourceId, resourceType, resourceName1, [resourceName2], ...)

Returns the resource ID for an extension resource. An extension resource is a resource type that's applied to another resource to add to its capabilities.

In Bicep, use the extensionResourceId function.

Parameters

Parameter Required Type Description
baseResourceId Yes string The resource ID for the resource that the extension resource is applied to.
resourceType Yes string Type of the extension resource including resource provider namespace.
resourceName1 Yes string Name of the extension resource.
resourceName2 No string Next resource name segment, if needed.

Continue adding resource names as parameters when the resource type includes more segments.

Return value

The basic format of the resource ID returned by this function is:

{scope}/providers/{extensionResourceProviderNamespace}/{extensionResourceType}/{extensionResourceName}

The scope segment varies by the base resource being extended. For example, the ID for a subscription has different segments than the ID for a resource group.

When the extension resource is applied to a resource, the resource ID is returned in the following format:

/subscriptions/{subscriptionId}/resourceGroups/{resourceGroupName}/providers/{baseResourceProviderNamespace}/{baseResourceType}/{baseResourceName}/providers/{extensionResourceProviderNamespace}/{extensionResourceType}/{extensionResourceName}

When the extension resource is applied to a resource group, the returned format is:

/subscriptions/{subscriptionId}/resourceGroups/{resourceGroupName}/providers/{extensionResourceProviderNamespace}/{extensionResourceType}/{extensionResourceName}

An example of using this function with a resource group is shown in the next section.

When the extension resource is applied to a subscription, the returned format is:

/subscriptions/{subscriptionId}/providers/{extensionResourceProviderNamespace}/{extensionResourceType}/{extensionResourceName}

When the extension resource is applied to a management group, the returned format is:

/providers/Microsoft.Management/managementGroups/{managementGroupName}/providers/{extensionResourceProviderNamespace}/{extensionResourceType}/{extensionResourceName}

An example of using this function with a management group is shown in the next section.

extensionResourceId example

The following example returns the resource ID for a resource group lock.

{
  "$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
  "contentVersion": "1.0.0.0",
  "parameters": {
    "lockName": {
      "type": "string"
    }
  },
  "variables": {},
  "resources": [],
  "outputs": {
    "lockResourceId": {
      "type": "string",
      "value": "[extensionResourceId(resourceGroup().Id , 'Microsoft.Authorization/locks', parameters('lockName'))]"
    }
  }
}

A custom policy definition deployed to a management group is implemented as an extension resource. To create and assign a policy, deploy the following template to a management group.

{
  "$schema": "https://schema.management.azure.com/schemas/2019-08-01/managementGroupDeploymentTemplate.json#",
  "contentVersion": "1.0.0.0",
  "metadata": {
    "_generator": {
      "name": "bicep",
      "version": "0.5.6.12127",
      "templateHash": "1532257987028557958"
    }
  },
  "parameters": {
    "targetMG": {
      "type": "string",
      "metadata": {
        "description": "Target Management Group"
      }
    },
    "allowedLocations": {
      "type": "array",
      "defaultValue": [
        "chinanorth2",
        "chinanorth3",
        "chinanorth"
      ],
      "metadata": {
        "description": "An array of the allowed locations, all other locations will be denied by the created policy."
      }
    }
  },
  "variables": {
    "mgScope": "[tenantResourceId('Microsoft.Management/managementGroups', parameters('targetMG'))]",
    "policyDefinitionName": "LocationRestriction"
  },
  "resources": [
    {
      "type": "Microsoft.Authorization/policyDefinitions",
      "apiVersion": "2020-03-01",
      "name": "[variables('policyDefinitionName')]",
      "properties": {
        "policyType": "Custom",
        "mode": "All",
        "parameters": {},
        "policyRule": {
          "if": {
            "not": {
              "field": "location",
              "in": "[parameters('allowedLocations')]"
            }
          },
          "then": {
            "effect": "deny"
          }
        }
      }
    },
    {
      "type": "Microsoft.Authorization/policyAssignments",
      "apiVersion": "2020-03-01",
      "name": "location-lock",
      "properties": {
        "scope": "[variables('mgScope')]",
        "policyDefinitionId": "[extensionResourceId(variables('mgScope'), 'Microsoft.Authorization/policyDefinitions', variables('policyDefinitionName'))]"
      },
      "dependsOn": [
        "[extensionResourceId(managementGroup().id, 'Microsoft.Authorization/policyDefinitions', variables('policyDefinitionName'))]"
      ]
    }
  ]
}

Built-in policy definitions are tenant level resources. For an example of deploying a built-in policy definition, see tenantResourceId.

list*

list{Value}(resourceName or resourceIdentifier, apiVersion, functionValues)

The syntax for this function varies by name of the list operations. Each implementation returns values for the resource type that supports a list operation. The operation name must start with list and may have a suffix. Some common usages are list, listKeys, listKeyValue, and listSecrets.

In Bicep, use the list* function.

Parameters

Parameter Required Type Description
resourceName or resourceIdentifier Yes string Unique identifier for the resource.
apiVersion Yes string API version of resource runtime state. Typically, in the format, yyyy-mm-dd.
functionValues No object An object that has values for the function. Only provide this object for functions that support receiving an object with parameter values, such as listAccountSas on a storage account. An example of passing function values is shown in this article.

Valid uses

The list functions can be used in the properties of a resource definition. Don't use a list function that exposes sensitive information in the outputs section of a template. Output values are stored in the deployment history and could be retrieved by a malicious user.

When used with property iteration, you can use the list functions for input because the expression is assigned to the resource property. You can't use them with count because the count must be determined before the list function is resolved.

Implementations

The possible uses of list* are shown in the following table.

Resource type Function name
Microsoft.Addons/supportProviders listsupportplaninfo
Microsoft.AnalysisServices/servers listGatewayStatus
Microsoft.ApiManagement/service/authorizationServers listSecrets
Microsoft.ApiManagement/service/gateways listKeys
Microsoft.ApiManagement/service/identityProviders listSecrets
Microsoft.ApiManagement/service/namedValues listValue
Microsoft.ApiManagement/service/openidConnectProviders listSecrets
Microsoft.ApiManagement/service/subscriptions listSecrets
Microsoft.AppConfiguration/configurationStores ListKeys
Microsoft.AppPlatform/Spring listTestKeys
Microsoft.Automation/automationAccounts listKeys
Microsoft.Batch/batchAccounts listKeys
Microsoft.CognitiveServices/accounts listKeys
Microsoft.CognitiveServices/accounts listKeys
Microsoft.ContainerRegistry/registries listCredentials
Microsoft.ContainerRegistry/registries listUsages
Microsoft.ContainerRegistry/registries/agentpools listQueueStatus
Microsoft.ContainerRegistry/registries/buildTasks listSourceRepositoryProperties
Microsoft.ContainerRegistry/registries/buildTasks/steps listBuildArguments
Microsoft.ContainerRegistry/registries/taskruns listDetails
Microsoft.ContainerRegistry/registries/webhooks listEvents
Microsoft.ContainerRegistry/registries/runs listLogSasUrl
Microsoft.ContainerRegistry/registries/tasks listDetails
Microsoft.ContainerService/managedClusters listClusterAdminCredential
Microsoft.ContainerService/managedClusters listClusterMonitoringUserCredential
Microsoft.ContainerService/managedClusters listClusterUserCredential
Microsoft.ContainerService/managedClusters/accessProfiles listCredential
Microsoft.DataBox/jobs listCredentials
Microsoft.DataFactory/datafactories/gateways listauthkeys
Microsoft.DataFactory/factories/integrationruntimes listauthkeys
Microsoft.Devices/iotHubs listKeys
Microsoft.Devices/iotHubs/iotHubKeys listKeys
Microsoft.Devices/provisioningServices/keys listKeys
Microsoft.Devices/provisioningServices listKeys
Microsoft.DevTestLab/labs/users/serviceFabrics ListApplicableSchedules
Microsoft.DocumentDB/databaseAccounts listKeys
Microsoft.DocumentDB/databaseAccounts/notebookWorkspaces listConnectionInfo
Microsoft.DomainRegistration/topLevelDomains listAgreements
Microsoft.EventHub/namespaces/authorizationRules listKeys
Microsoft.EventHub/namespaces/disasterRecoveryConfigs/authorizationRules listKeys
Microsoft.EventHub/namespaces/eventhubs/authorizationRules listKeys
Microsoft.ImportExport/jobs listBitLockerKeys
Microsoft.Kusto/Clusters/Databases ListPrincipals
Microsoft.Logic/integrationAccounts/agreements listContentCallbackUrl
Microsoft.Logic/integrationAccounts/assemblies listContentCallbackUrl
Microsoft.Logic/integrationAccounts listCallbackUrl
Microsoft.Logic/integrationAccounts listKeyVaultKeys
Microsoft.Logic/integrationAccounts/maps listContentCallbackUrl
Microsoft.Logic/integrationAccounts/partners listContentCallbackUrl
Microsoft.Logic/integrationAccounts/schemas listContentCallbackUrl
Microsoft.Logic/workflows listCallbackUrl
Microsoft.Logic/workflows listSwagger
Microsoft.Logic/workflows/runs/actions listExpressionTraces
Microsoft.Logic/workflows/runs/actions/repetitions listExpressionTraces
Microsoft.Logic/workflows/triggers listCallbackUrl
Microsoft.Logic/workflows/versions/triggers listCallbackUrl
Microsoft.Media/mediaservices/assets listContainerSas
Microsoft.Media/mediaservices/assets listStreamingLocators
Microsoft.Media/mediaservices/streamingLocators listContentKeys
Microsoft.Media/mediaservices/streamingLocators listPaths
Microsoft.Network/applicationSecurityGroups listIpConfigurations
Microsoft.NotificationHubs/Namespaces/authorizationRules listkeys
Microsoft.NotificationHubs/Namespaces/NotificationHubs/authorizationRules listkeys
Microsoft.OperationalInsights/workspaces list
Microsoft.OperationalInsights/workspaces listKeys
Microsoft.PolicyInsights/remediations listDeployments
Microsoft.Relay/namespaces/authorizationRules listKeys
Microsoft.Relay/namespaces/disasterRecoveryConfigs/authorizationRules listKeys
Microsoft.Relay/namespaces/HybridConnections/authorizationRules listKeys
Microsoft.Relay/namespaces/WcfRelays/authorizationRules listkeys
Microsoft.Search/searchServices listAdminKeys
Microsoft.Search/searchServices listQueryKeys
Microsoft.ServiceBus/namespaces/authorizationRules listKeys
Microsoft.ServiceBus/namespaces/disasterRecoveryConfigs/authorizationRules listKeys
Microsoft.ServiceBus/namespaces/queues/authorizationRules listKeys
Microsoft.SignalRService/SignalR listKeys
Microsoft.Storage/storageAccounts listAccountSas
Microsoft.Storage/storageAccounts listKeys
Microsoft.Storage/storageAccounts listServiceSas
Microsoft.Synapse/workspaces/integrationRuntimes listAuthKeys
Microsoft.Web/connectionGateways ListStatus
microsoft.web/connections listconsentlinks
Microsoft.Web/customApis listWsdlInterfaces
microsoft.web/locations listwsdlinterfaces
microsoft.web/apimanagementaccounts/apis/connections listconnectionkeys
microsoft.web/apimanagementaccounts/apis/connections listSecrets
microsoft.web/sites/backups list
Microsoft.Web/sites/config list
microsoft.web/sites/functions listKeys
microsoft.web/sites/functions listSecrets
microsoft.web/sites/hybridconnectionnamespaces/relays listKeys
microsoft.web/sites listsyncfunctiontriggerstatus
microsoft.web/sites/slots/functions listSecrets
microsoft.web/sites/slots/backups list
Microsoft.Web/sites/slots/config list
microsoft.web/sites/slots/functions listSecrets

To determine which resource types have a list operation, you have the following options:

  • View the REST API operations for a resource provider, and look for list operations. For example, storage accounts have the listKeys operation.

  • Use the Get-​AzProvider​Operation PowerShell cmdlet. The following example gets all list operations for storage accounts:

    Get-AzProviderOperation -OperationSearchString "Microsoft.Storage/*" | where {$_.Operation -like "*list*"} | FT Operation

  • Use the following Azure CLI command to filter only the list operations:

    az provider operation show --namespace Microsoft.Storage --query "resourceTypes[?name=='storageAccounts'].operations[].name | [?contains(@, 'list')]"

Return value

The returned object varies by the list function you use. For example, the listKeys for a storage account returns the following format:

{
  "keys": [
    {
      "keyName": "key1",
      "permissions": "Full",
      "value": "{value}"
    },
    {
      "keyName": "key2",
      "permissions": "Full",
      "value": "{value}"
    }
  ]
}

Other list functions have different return formats. To see the format of a function, include it in the outputs section as shown in the example template.

Remarks

Specify the resource by using either the resource name or the resourceId function. When using a list function in the same template that deploys the referenced resource, use the resource name.

If you use a list function in a resource that is conditionally deployed, the function is evaluated even if the resource isn't deployed. You get an error if the list function refers to a resource that doesn't exist. Use the if function to make sure the function is only evaluated when the resource is being deployed. See the if function for a sample template that uses if and list with a conditionally deployed resource.

List example

The following example uses listKeys when setting a value for deployment scripts.

"storageAccountSettings": {
  "storageAccountName": "[variables('storageAccountName')]",
  "storageAccountKey": "[listKeys(resourceId('Microsoft.Storage/storageAccounts', variables('storageAccountName')), '2019-06-01').keys[0].value]"
}

The next example shows a list function that takes a parameter. In this case, the function is listAccountSas. Pass an object for the expiry time. The expiry time must be in the future.

"parameters": {
  "accountSasProperties": {
    "type": "object",
    "defaultValue": {
      "signedServices": "b",
      "signedPermission": "r",
      "signedExpiry": "2020-08-20T11:00:00Z",
      "signedResourceTypes": "s"
    }
  }
},
...
"sasToken": "[listAccountSas(parameters('storagename'), '2018-02-01', parameters('accountSasProperties')).accountSasToken]"

pickZones

pickZones(providerNamespace, resourceType, location, [numberOfZones], [offset])

Determines whether a resource type supports zones for the specified location or region. This function only supports zonal resources. Zone redundant services return an empty array. For more information, see Azure Services that support Availability Zones.

In Bicep, use the pickZones function.

Parameters

Parameter Required Type Description
providerNamespace Yes string The resource provider namespace for the resource type to check for zone support.
resourceType Yes string The resource type to check for zone support.
location Yes string The region to check for zone support.
numberOfZones No integer The number of logical zones to return. The default is 1. The number must be a positive integer from 1 to 3. Use 1 for single-zoned resources. For multi-zoned resources, the value must be less than or equal to the number of supported zones.
offset No integer The offset from the starting logical zone. The function returns an error if offset plus numberOfZones exceeds the number of supported zones.

Return value

An array with the supported zones. When using the default values for offset and numberOfZones, a resource type and region that supports zones returns the following array:

[
    "1"
]

When the numberOfZones parameter is set to 3, it returns:

[
    "1",
    "2",
    "3"
]

When the resource type or region doesn't support zones, an empty array is returned. An empty array is also returned for zone redundant services.

[
]

Remarks

There are different categories for Azure Availability Zones - zonal and zone-redundant. The pickZones function can be used to return an availability zone for a zonal resource. For zone redundant services (ZRS), the function returns an empty array. Zonal resources typically have a zones property at the top level of the resource definition. To determine the category of support for availability zones, see Azure Services that support Availability Zones.

To determine if a given Azure region or location supports availability zones, call the pickZones function with a zonal resource type, such as Microsoft.Network/publicIPAddresses. If the response isn't empty, the region supports availability zones.

pickZones example

The following template shows three results for using the pickZones function.

{
  "$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
  "contentVersion": "1.0.0.0",
  "parameters": {},
  "functions": [],
  "variables": {},
  "resources": [],
  "outputs": {
    "supported": {
      "type": "array",
      "value": "[pickZones('Microsoft.Compute', 'virtualMachines', 'chinaeast2')]"
    },
    "notSupportedRegion": {
      "type": "array",
      "value": "[pickZones('Microsoft.Compute', 'virtualMachines', 'chinanorth')]"
    },
    "notSupportedType": {
      "type": "array",
      "value": "[pickZones('Microsoft.Cdn', 'profiles', 'chinaeast2')]"
    }
  }
}

The output from the preceding examples returns three arrays.

Name Type Value
supported array [ "1" ]
notSupportedRegion array []
notSupportedType array []

You can use the response from pickZones to determine whether to provide null for zones or assign virtual machines to different zones. The following example sets a value for the zone based on the availability of zones.

"zones": {
  "value": "[if(not(empty(pickZones('Microsoft.Compute', 'virtualMachines', 'chinanorth2'))), string(add(mod(copyIndex(),3),1)), json('null'))]"
},

Azure Cosmos DB isn't a zonal resource, but you can use the pickZones function to determine whether to enable zone redundancy for georeplication. Pass the Microsoft.Storage/storageAccounts resource type to determine whether to enable zone redundancy.

"resources": [
  {
    "type": "Microsoft.DocumentDB/databaseAccounts",
    "apiVersion": "2021-04-15",
    "name": "[variables('accountName_var')]",
    "location": "[parameters('location')]",
    "kind": "GlobalDocumentDB",
    "properties": {
      "consistencyPolicy": "[variables('consistencyPolicy')[parameters('defaultConsistencyLevel')]]",
      "locations": [
        {
          "locationName": "[parameters('primaryRegion')]",
          "failoverPriority": 0,
          "isZoneRedundant": "[if(empty(pickZones('Microsoft.Storage', 'storageAccounts', parameters('primaryRegion'))), bool('false'), bool('true'))]",
        },
        {
          "locationName": "[parameters('secondaryRegion')]",
          "failoverPriority": 1,
          "isZoneRedundant": "[if(empty(pickZones('Microsoft.Storage', 'storageAccounts', parameters('secondaryRegion'))), bool('false'), bool('true'))]",
        }
      ],
      "databaseAccountOfferType": "Standard",
      "enableAutomaticFailover": "[parameters('automaticFailover')]"
    }
  }
]

providers

The providers function has been deprecated in ARM templates. We no longer recommend using it. If you used this function to get an API version for the resource provider, we recommend that you provide a specific API version in your template. Using a dynamically returned API version can break your template if the properties change between versions.

In Bicep, the providers function is deprecated.

The providers operation is still available through the REST API. It can be used outside of an ARM template to get information about a resource provider.

reference

In the templates without symbolic names:

reference(resourceName or resourceIdentifier, [apiVersion], ['Full'])

In the templates with symbolic names:

reference(symbolicName or resourceIdentifier, [apiVersion], ['Full'])

Returns an object representing a resource's runtime state. The output and behavior of the reference function highly relies on how each resource provider (RP) implements its PUT and GET responses. To return an array of objects representing a resource collections's runtime states, see references.

Bicep provides the reference function, but in most cases, the reference function isn't required. It's recommended to use the symbolic name for the resource instead. See reference.

Parameters

Parameter Required Type Description
resourceName/resourceIdentifier or symbolicName/resourceIdentifier Yes string In the templates without symbolic names, specify name or unique identifier of a resource. When referencing a resource in the current template, provide only the resource name as a parameter. When referencing a previously deployed resource or when the name of the resource is ambiguous, provide the resource ID.
In the templates with symbolic names, specify symbolic name or unique identifier of a resource. When referencing a resource in the current template, provide only the resource symbolic name as a parameter. When referencing a previously deployed resource, provide the resource ID.
apiVersion No string API version of the specified resource. This parameter is required when the resource isn't provisioned within same template. Typically, in the format, yyyy-mm-dd.
'Full' No string Value that specifies whether to return the full resource object. If you don't specify 'Full', only the properties object of the resource is returned. The full object includes values such as the resource ID and location.

Return value

Every resource type returns different properties for the reference function. The function doesn't return a single, predefined format. Also, the returned value differs based on the value of the 'Full' argument. To see the properties for a resource type, return the object in the outputs section as shown in the example.

Remarks

The reference function retrieves the runtime state of either a previously deployed resource or a resource deployed in the current template. This article shows examples for both scenarios.

Typically, you use the reference function to return a particular value from an object, such as the blob endpoint URI or fully qualified domain name.

"outputs": {
  "BlobUri": {
    "type": "string",
    "value": "[reference(resourceId('Microsoft.Storage/storageAccounts', parameters('storageAccountName'))).primaryEndpoints.blob]"
  },
  "FQDN": {
    "type": "string",
    "value": "[reference(resourceId('Microsoft.Network/publicIPAddresses', parameters('ipAddressName'))).dnsSettings.fqdn]"
  }
}

Use 'Full' when you need resource values that aren't part of the properties schema. For example, to set key vault access policies, get the identity properties for a virtual machine.

{
  "type": "Microsoft.KeyVault/vaults",
  "apiVersion": "2022-07-01",
  "name": "vaultName",
  "properties": {
    "tenantId": "[subscription().tenantId]",
    "accessPolicies": [
      {
        "tenantId": "[reference(resourceId('Microsoft.Compute/virtualMachines', variables('vmName')), '2019-03-01', 'Full').identity.tenantId]",
        "objectId": "[reference(resourceId('Microsoft.Compute/virtualMachines', variables('vmName')), '2019-03-01', 'Full').identity.principalId]",
        "permissions": {
          "keys": [
            "all"
          ],
          "secrets": [
            "all"
          ]
        }
      }
    ],
    ...

Valid uses

The reference function can only be used in the outputs section of a template or deployment and properties object of a resource definition. It cannot be used for resource properties such as type, name, location and other top level properties of the resource definition. When used with property iteration, you can use the reference function for input because the expression is assigned to the resource property.

You can't use the reference function to set the value of the count property in a copy loop. You can use to set other properties in the loop. Reference is blocked for the count property because that property must be determined before the reference function is resolved.

To use the reference function or any list* function in the outputs section of a nested template, you must set the expressionEvaluationOptions to use inner scope evaluation or use a linked instead of a nested template.

If you use the reference function in a resource that is conditionally deployed, the function is evaluated even if the resource isn't deployed. You get an error if the reference function refers to a resource that doesn't exist. Use the if function to make sure the function is only evaluated when the resource is being deployed. See the if function for a sample template that uses if and reference with a conditionally deployed resource.

Implicit dependency

By using the reference function, you implicitly declare that one resource depends on another resource if the referenced resource is provisioned within same template and you refer to the resource by its name (not resource ID). You don't need to also use the dependsOn property. The function isn't evaluated until the referenced resource has completed deployment.

Resource name, Symbolic name or identifier

When referencing a resource that is deployed in the same none-symbolic-name template, provide the name of the resource.

"value": "[reference(parameters('storageAccountName'))]"

When referencing a resource that is deployed in the same symbolic-name template, provide the symbolic name of the resource.

"value": "[reference('myStorage').primaryEndpoints]"

Or

"value": "[reference('myStorage', '2022-09-01', 'Full').location]"

When referencing a resource that isn't deployed in the same template, provide the resource ID and apiVersion.

"value": "[reference(resourceId(parameters('storageResourceGroup'), 'Microsoft.Storage/storageAccounts', parameters('storageAccountName')), '2022-09-01')]"

To avoid ambiguity about which resource you're referencing, you can provide a fully qualified resource identifier.

"value": "[reference(resourceId('Microsoft.Network/publicIPAddresses', parameters('ipAddressName')))]"

When constructing a fully qualified reference to a resource, the order to combine segments from the type and name isn't simply a concatenation of the two. Instead, after the namespace, use a sequence of type/name pairs from least specific to most specific:

{resource-provider-namespace}/{parent-resource-type}/{parent-resource-name}[/{child-resource-type}/{child-resource-name}]

For example:

Microsoft.Compute/virtualMachines/myVM/extensions/myExt is correct Microsoft.Compute/virtualMachines/extensions/myVM/myExt is not correct

To simplify the creation of any resource ID, use the resourceId() functions described in this document instead of the concat() function.

Get managed identity

Managed identities for Azure resources are extension resource types that are created implicitly for some resources. Because the managed identity isn't explicitly defined in the template, you must reference the resource that the identity is applied to. Use Full to get all of the properties, including the implicitly created identity.

The pattern is:

"[reference(resourceId(<resource-provider-namespace>, <resource-name>), <API-version>, 'Full').Identity.propertyName]"

For example, to get the principal ID for a managed identity that is applied to a virtual machine, use:

"[reference(resourceId('Microsoft.Compute/virtualMachines', variables('vmName')),'2019-12-01', 'Full').identity.principalId]",

Or, to get the tenant ID for a managed identity that is applied to a virtual machine scale set, use:

"[reference(resourceId('Microsoft.Compute/virtualMachineScaleSets',  variables('vmNodeType0Name')), 2019-12-01, 'Full').Identity.tenantId]"

Reference example

The following example deploys a resource, and references that resource.

{
  "$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
  "contentVersion": "1.0.0.0",
  "parameters": {
    "storageAccountName": {
      "type": "string"
    },
    "location": {
      "type": "string",
      "defaultValue": "[resourceGroup().location]"
    }
  },
  "resources": [
    {
      "type": "Microsoft.Storage/storageAccounts",
      "apiVersion": "2022-09-01",
      "name": "[parameters('storageAccountName')]",
      "location": "[parameters('location')]",
      "sku": {
        "name": "Standard_LRS"
      },
      "kind": "Storage",
      "tags": {},
      "properties": {
      }
    }
  ],
  "outputs": {
    "referenceOutput": {
      "type": "object",
      "value": "[reference(parameters('storageAccountName'))]"
    },
    "fullReferenceOutput": {
      "type": "object",
      "value": "[reference(parameters('storageAccountName'), '2022-09-01', 'Full')]"
    }
  }
}

The preceding example returns the two objects. The properties object is in the following format:

{
   "creationTime": "2017-10-09T18:55:40.5863736Z",
   "primaryEndpoints": {
     "blob": "https://examplestorage.blob.core.chinacloudapi.cn/",
     "file": "https://examplestorage.file.core.chinacloudapi.cn/",
     "queue": "https://examplestorage.queue.core.chinacloudapi.cn/",
     "table": "https://examplestorage.table.core.chinacloudapi.cn/"
   },
   "primaryLocation": "chinanorth3",
   "provisioningState": "Succeeded",
   "statusOfPrimary": "available",
   "supportsHttpsTrafficOnly": false
}

The full object is in the following format:

{
  "apiVersion":"2022-09-01",
  "location":"southchinanorth2",
  "sku": {
    "name":"Standard_LRS",
    "tier":"Standard"
  },
  "tags":{},
  "kind":"Storage",
  "properties": {
    "creationTime":"2021-10-09T18:55:40.5863736Z",
    "primaryEndpoints": {
      "blob":"https://examplestorage.blob.core.chinacloudapi.cn/",
      "file":"https://examplestorage.file.core.chinacloudapi.cn/",
      "queue":"https://examplestorage.queue.core.chinacloudapi.cn/",
      "table":"https://examplestorage.table.core.chinacloudapi.cn/"
    },
    "primaryLocation":"chinanorth3",
    "provisioningState":"Succeeded",
    "statusOfPrimary":"available",
    "supportsHttpsTrafficOnly":false
  },
  "subscriptionId":"<subscription-id>",
  "resourceGroupName":"functionexamplegroup",
  "resourceId":"Microsoft.Storage/storageAccounts/examplestorage",
  "referenceApiVersion":"2021-04-01",
  "condition":true,
  "isConditionTrue":true,
  "isTemplateResource":false,
  "isAction":false,
  "provisioningOperation":"Read"
}

The following example template references a storage account that isn't deployed in this template. The storage account already exists within the same subscription.

{
  "$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
  "contentVersion": "1.0.0.0",
  "parameters": {
    "storageResourceGroup": {
      "type": "string"
    },
    "storageAccountName": {
      "type": "string"
    }
  },
  "resources": [],
  "outputs": {
    "ExistingStorage": {
      "type": "object",
      "value": "[reference(resourceId(parameters('storageResourceGroup'), 'Microsoft.Storage/storageAccounts', parameters('storageAccountName')), '2021-04-01')]"
    }
  }
}

references

references(symbolic name of a resource collection, ['Full', 'Properties])

The references function works similarly as reference. Instead of returning an object presenting a resource's runtime state, the references function returns an array of objects representing a resource collection's runtime states. This function requires ARM template language version 2.0 and with symbolic name enabled:

{
  "$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
  "languageVersion": "2.0",
  "contentVersion": "1.0.0.0",
  ...
}

In Bicep, there is no explicit references function. Instead, symbolic collection usage is employed directly, and during code generation, Bicep translates it to an ARM template that utilizes the ARM template references function. For more information, see Reference resource/module collections.

Parameters

Parameter Required Type Description
Symbolic name of a resource collection Yes string Symbolic name of a resource collection that is defined in the current template. The references function does not support referencing resources external to the current template.
'Full', 'Properties' No string Value that specifies whether to return an array of the full resource objects. The default value is 'Properties'. If you don't specify 'Full', only the properties objects of the resources are returned. The full object includes values such as the resource ID and location.

Return value

An array of the resource collection. Every resource type returns different properties for the reference function. Also, the returned value differs based on the value of the 'Full' argument. For more information, see reference.

The output order of references is always arranged in ascending order based on the copy index. Therefore, the first resource in the collection with index 0 is displayed first, followed by index 1, and so on. For instance, [worker-0, worker-1, worker-2, ...].

In the preceding example, if worker-0 and worker-2 are deployed while worker-1 is not due to a false condition, the output of references will omit the non-deployed resource and display the deployed ones, ordered by their numbers. The output of references will be [worker-0, worker-2, ...]. If all of the resources are omitted, the function returns an empty array.

Valid uses

The references function can't be used within resource copy loops or Bicep for loop. For example, references is not allowed in the following scenario:

{
  resources: {
    "resourceCollection": {
       "copy": { ... },
       "properties": {
         "prop": "[references(...)]"
       }
    }
  }
}

To use the references function or any list* function in the outputs section of a nested template, you must set the expressionEvaluationOptions to use inner scope evaluation or use a linked instead of a nested template.

Implicit dependency

By using the references function, you implicitly declare that one resource depends on another resource. You don't need to also use the dependsOn property. The function isn't evaluated until the referenced resource has completed deployment.

Reference example

The following example deploys a resource collection, and references that resource collection.

{
  "$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
  "languageVersion": "2.0",
  "contentVersion": "1.0.0.0",
  "parameters": {
    "location": {
      "type": "string",
      "defaultValue": "[resourceGroup().location]",
      "metadata": {
        "description": "Location for all resources."
      }
    },
    "numWorkers": {
      "type": "int",
      "defaultValue": 4,
      "metadata": {
        "description": "The number of workers"
      }
    }
  },
  "resources": {
    "containerWorkers": {
      "copy": {
        "name": "containerWorkers",
        "count": "[length(range(0, parameters('numWorkers')))]"
      },
      "type": "Microsoft.ContainerInstance/containerGroups",
      "apiVersion": "2023-05-01",
      "name": "[format('worker-{0}', range(0, parameters('numWorkers'))[copyIndex()])]",
      "location": "[parameters('location')]",
      "properties": {
        "containers": [
          {
            "name": "[format('worker-container-{0}', range(0, parameters('numWorkers'))[copyIndex()])]",
            "properties": {
              "image": "mcr.microsoft.com/azuredocs/aci-helloworld",
              "ports": [
                {
                  "port": 80,
                  "protocol": "TCP"
                }
              ],
              "resources": {
                "requests": {
                  "cpu": 1,
                  "memoryInGB": 2
                }
              }
            }
          }
        ],
        "osType": "Linux",
        "restartPolicy": "Always",
        "ipAddress": {
          "type": "Public",
          "ports": [
            {
              "port": 80,
              "protocol": "TCP"
            }
          ]
        }
      }
    },
    "containerController": {
      "type": "Microsoft.ContainerInstance/containerGroups",
      "apiVersion": "2023-05-01",
      "name": "controller",
      "location": "[parameters('location')]",
      "properties": {
        "containers": [
          {
            "name": "controller-container",
            "properties": {
              "command": [
                "echo",
                "[format('Worker IPs are {0}', join(map(references('containerWorkers', 'full'), lambda('w', lambdaVariables('w').properties.ipAddress.ip)), ','))]"
              ],
              "image": "mcr.microsoft.com/azuredocs/aci-helloworld",
              "ports": [
                {
                  "port": 80,
                  "protocol": "TCP"
                }
              ],
              "resources": {
                "requests": {
                  "cpu": 1,
                  "memoryInGB": 2
                }
              }
            }
          }
        ],
        "osType": "Linux",
        "restartPolicy": "Always",
        "ipAddress": {
          "type": "Public",
          "ports": [
            {
              "port": 80,
              "protocol": "TCP"
            }
          ]
        }
      },
      "dependsOn": [
        "containerWorkers"
      ]
    }
  },
  "outputs": {
    "workerIpAddresses": {
      "type": "string",
      "value": "[join(map(references('containerWorkers', 'full'), lambda('w', lambdaVariables('w').properties.ipAddress.ip)), ',')]"
    },
    "containersFull": {
      "type": "array",
      "value": "[references('containerWorkers', 'full')]"
    },
    "container": {
      "type": "array",
      "value": "[references('containerWorkers')]"
    }
  }
}

The preceding example returns the three objects.

"outputs": {
  "workerIpAddresses": {
    "type": "String",
    "value": "20.66.74.26,20.245.100.10,13.91.86.58,40.83.249.30"
  },
  "containersFull": {
    "type": "Array",
    "value": [
      {
        "apiVersion": "2023-05-01",
        "condition": true,
        "copyContext": {
          "copyIndex": 0,
          "copyIndexes": {
            "": 0,
            "containerWorkers": 0
          },
          "name": "containerWorkers"
        },
        "copyLoopSymbolicName": "containerWorkers",
        "deploymentResourceLineInfo": {
          "lineNumber": 30,
          "linePosition": 25
        },
        "existing": false,
        "isAction": false,
        "isConditionTrue": true,
        "isTemplateResource": true,
        "location": "westus",
        "properties": {
          "containers": [
            {
              "name": "worker-container-0",
              "properties": {
                "environmentVariables": [],
                "image": "mcr.microsoft.com/azuredocs/aci-helloworld",
                "instanceView": {
                  "currentState": {
                    "detailStatus": "",
                    "startTime": "2023-07-31T19:25:31.996Z",
                    "state": "Running"
                  },
                  "restartCount": 0
                },
                "ports": [
                  {
                    "port": 80,
                    "protocol": "TCP"
                  }
                ],
                "resources": {
                  "requests": {
                    "cpu": 1.0,
                    "memoryInGB": 2.0
                  }
                }
              }
            }
          ],
          "initContainers": [],
          "instanceView": {
            "events": [],
            "state": "Running"
          },
          "ipAddress": {
            "ip": "20.66.74.26",
            "ports": [
              {
                "port": 80,
                "protocol": "TCP"
              }
            ],
            "type": "Public"
          },
          "isCustomProvisioningTimeout": false,
          "osType": "Linux",
          "provisioningState": "Succeeded",
          "provisioningTimeoutInSeconds": 1800,
          "restartPolicy": "Always",
          "sku": "Standard"
        },
        "provisioningOperation": "Create",
        "references": [],
        "resourceGroupName": "demoRg",
        "resourceId": "Microsoft.ContainerInstance/containerGroups/worker-0",
        "scope": "",
        "subscriptionId": "",
        "symbolicName": "containerWorkers[0]"
      },
      ...
    ]
  },
  "containers": {
    "type": "Array",
    "value": [
      {
        "containers": [
          {
            "name": "worker-container-0",
            "properties": {
              "environmentVariables": [],
              "image": "mcr.microsoft.com/azuredocs/aci-helloworld",
              "instanceView": {
                "currentState": {
                  "detailStatus": "",
                  "startTime": "2023-07-31T19:25:31.996Z",
                  "state": "Running"
                },
                "restartCount": 0
              },
              "ports": [
                {
                  "port": 80,
                  "protocol": "TCP"
                }
              ],
              "resources": {
                "requests": {
                  "cpu": 1.0,
                  "memoryInGB": 2.0
                }
              }
            }
          }
        ],
        "initContainers": [],
        "instanceView": {
          "events": [],
          "state": "Running"
        },
        "ipAddress": {
          "ip": "20.66.74.26",
          "ports": [
            {
              "port": 80,
              "protocol": "TCP"
            }
          ],
          "type": "Public"
        },
        "isCustomProvisioningTimeout": false,
        "osType": "Linux",
        "provisioningState": "Succeeded",
        "provisioningTimeoutInSeconds": 1800,
        "restartPolicy": "Always",
        "sku": "Standard"
      },
      ...
    ]
  }
}

resourceGroup

See the resourceGroup scope function.

In Bicep, use the resourcegroup scope function.

resourceId

resourceId([subscriptionId], [resourceGroupName], resourceType, resourceName1, [resourceName2], ...)

Returns the unique identifier of a resource. You use this function when the resource name is ambiguous or not provisioned within the same template. The format of the returned identifier varies based on whether the deployment happens at the scope of a resource group, subscription, management group, or tenant.

In Bicep, use the resourceId function.

Parameters

Parameter Required Type Description
subscriptionId No string (In GUID format) Default value is the current subscription. Specify this value when you need to retrieve a resource in another subscription. Only provide this value when deploying at the scope of a resource group or subscription.
resourceGroupName No string Default value is current resource group. Specify this value when you need to retrieve a resource in another resource group. Only provide this value when deploying at the scope of a resource group.
resourceType Yes string Type of resource including resource provider namespace.
resourceName1 Yes string Name of resource.
resourceName2 No string Next resource name segment, if needed.

Continue adding resource names as parameters when the resource type includes more segments.

Return value

The resource ID is returned in different formats at different scopes:

  • Resource group scope:

    /subscriptions/{subscriptionId}/resourceGroups/{resourceGroupName}/providers/{resourceProviderNamespace}/{resourceType}/{resourceName}

  • Subscription scope:

    /subscriptions/{subscriptionId}/providers/{resourceProviderNamespace}/{resourceType}/{resourceName}

  • Management group or tenant scope:

    /providers/{resourceProviderNamespace}/{resourceType}/{resourceName}

To avoid confusion, we recommend that you don't use resourceId when working with resources deployed to the subscription, management group, or tenant. Instead, use the ID function that is designed for the scope.

Remarks

The number of parameters you provide varies based on whether the resource is a parent or child resource, and whether the resource is in the same subscription or resource group.

To get the resource ID for a parent resource in the same subscription and resource group, provide the type and name of the resource.

"[resourceId('Microsoft.ServiceBus/namespaces', 'namespace1')]"

To get the resource ID for a child resource, pay attention to the number of segments in the resource type. Provide a resource name for each segment of the resource type. The name of the segment corresponds to the resource that exists for that part of the hierarchy.

"[resourceId('Microsoft.ServiceBus/namespaces/queues/authorizationRules', 'namespace1', 'queue1', 'auth1')]"

To get the resource ID for a resource in the same subscription but different resource group, provide the resource group name.

"[resourceId('otherResourceGroup', 'Microsoft.Storage/storageAccounts', 'examplestorage')]"

To get the resource ID for a resource in a different subscription and resource group, provide the subscription ID and resource group name.

"[resourceId('xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx', 'otherResourceGroup', 'Microsoft.Storage/storageAccounts','examplestorage')]"

Often, you need to use this function when using a storage account or virtual network in an alternate resource group. The following example shows how a resource from an external resource group can easily be used:

{
  "$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
  "contentVersion": "1.0.0.0",
  "parameters": {
    "location": {
      "type": "string"
    },
    "virtualNetworkName": {
      "type": "string"
    },
    "virtualNetworkResourceGroup": {
      "type": "string"
    },
    "subnet1Name": {
      "type": "string"
    },
    "nicName": {
      "type": "string"
    }
  },
  "variables": {
    "subnet1Ref": "[resourceId(parameters('virtualNetworkResourceGroup'), 'Microsoft.Network/virtualNetworks/subnets', parameters('virtualNetworkName'), parameters('subnet1Name'))]"
  },
  "resources": [
    {
      "type": "Microsoft.Network/networkInterfaces",
      "apiVersion": "2022-11-01",
      "name": "[parameters('nicName')]",
      "location": "[parameters('location')]",
      "properties": {
        "ipConfigurations": [
          {
            "name": "ipconfig1",
            "properties": {
              "privateIPAllocationMethod": "Dynamic",
              "subnet": {
                "id": "[variables('subnet1Ref')]"
              }
            }
          }
        ]
      }
    }
  ]
}

Resource ID example

The following example returns the resource ID for a storage account in the resource group:

{
  "$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
  "contentVersion": "1.0.0.0",
  "resources": [],
  "outputs": {
    "sameRGOutput": {
      "type": "string",
      "value": "[resourceId('Microsoft.Storage/storageAccounts','examplestorage')]"
    },
    "differentRGOutput": {
      "type": "string",
      "value": "[resourceId('otherResourceGroup', 'Microsoft.Storage/storageAccounts','examplestorage')]"
    },
    "differentSubOutput": {
      "type": "string",
      "value": "[resourceId('11111111-1111-1111-1111-111111111111', 'otherResourceGroup', 'Microsoft.Storage/storageAccounts','examplestorage')]"
    },
    "nestedResourceOutput": {
      "type": "string",
      "value": "[resourceId('Microsoft.SQL/servers/databases', 'serverName', 'databaseName')]"
    }
  }
}

The output from the preceding example with the default values is:

Name Type Value
sameRGOutput String /subscriptions/{current-sub-id}/resourceGroups/examplegroup/providers/Microsoft.Storage/storageAccounts/examplestorage
differentRGOutput String /subscriptions/{current-sub-id}/resourceGroups/otherResourceGroup/providers/Microsoft.Storage/storageAccounts/examplestorage
differentSubOutput String /subscriptions/aaaa0a0a-bb1b-cc2c-dd3d-eeeeee4e4e4e/resourceGroups/otherResourceGroup/providers/Microsoft.Storage/storageAccounts/examplestorage
nestedResourceOutput String /subscriptions/{current-sub-id}/resourceGroups/examplegroup/providers/Microsoft.SQL/servers/serverName/databases/databaseName

subscription

See the subscription scope function.

In Bicep, use the subscription scope function.

subscriptionResourceId

subscriptionResourceId([subscriptionId], resourceType, resourceName1, [resourceName2], ...)

Returns the unique identifier for a resource deployed at the subscription level.

In Bicep, use the subscriptionResourceId function.

Parameters

Parameter Required Type Description
subscriptionId No string (in GUID format) Default value is the current subscription. Specify this value when you need to retrieve a resource in another subscription.
resourceType Yes string Type of resource including resource provider namespace.
resourceName1 Yes string Name of resource.
resourceName2 No string Next resource name segment, if needed.

Continue adding resource names as parameters when the resource type includes more segments.

Return value

The identifier is returned in the following format:

/subscriptions/{subscriptionId}/providers/{resourceProviderNamespace}/{resourceType}/{resourceName}

Remarks

You use this function to get the resource ID for resources that are deployed to the subscription rather than a resource group. The returned ID differs from the value returned by the resourceId function by not including a resource group value.

subscriptionResourceID example

The following template assigns a built-in role. You can deploy it to either a resource group or subscription. It uses the subscriptionResourceId function to get the resource ID for built-in roles.

{
  "$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
  "contentVersion": "1.0.0.0",
  "parameters": {
    "principalId": {
      "type": "string",
      "metadata": {
        "description": "The principal to assign the role to"
      }
    },
    "builtInRoleType": {
      "type": "string",
      "allowedValues": [
        "Owner",
        "Contributor",
        "Reader"
      ],
      "metadata": {
        "description": "Built-in role to assign"
      }
    },
    "roleNameGuid": {
      "type": "string",
      "defaultValue": "[newGuid()]",
      "metadata": {
        "description": "A new GUID used to identify the role assignment"
      }
    }
  },
  "variables": {
    "Owner": "[subscriptionResourceId('Microsoft.Authorization/roleDefinitions', '8e3af657-a8ff-443c-a75c-2fe8c4bcb635')]",
    "Contributor": "[subscriptionResourceId('Microsoft.Authorization/roleDefinitions', 'b24988ac-6180-42a0-ab88-20f7382dd24c')]",
    "Reader": "[subscriptionResourceId('Microsoft.Authorization/roleDefinitions', 'acdd72a7-3385-48ef-bd42-f606fba81ae7')]"
  },
  "resources": [
    {
      "type": "Microsoft.Authorization/roleAssignments",
      "apiVersion": "2022-04-01",
      "name": "[parameters('roleNameGuid')]",
      "properties": {
        "roleDefinitionId": "[variables(parameters('builtInRoleType'))]",
        "principalId": "[parameters('principalId')]"
      }
    }
  ]
}

managementGroupResourceId

managementGroupResourceId([managementGroupResourceId],resourceType, resourceName1, [resourceName2], ...)

Returns the unique identifier for a resource deployed at the management group level.

In Bicep, use the managementGroupResourceId function.

Parameters

Parameter Required Type Description
managementGroupResourceId No string (in GUID format) Default value is the current management group. Specify this value when you need to retrieve a resource in another management group.
resourceType Yes string Type of resource including resource provider namespace.
resourceName1 Yes string Name of resource.
resourceName2 No string Next resource name segment, if needed.

Continue adding resource names as parameters when the resource type includes more segments.

Return value

The identifier is returned in the following format:

/providers/Microsoft.Management/managementGroups/{managementGroupName}/providers/{resourceType}/{resourceName}

Remarks

You use this function to get the resource ID for resources that are deployed to the management group rather than a resource group. The returned ID differs from the value returned by the resourceId function by not including a subscription ID and a resource group value.

managementGroupResourceID example

The following template creates and assigns a policy definition. It uses the managementGroupResourceId function to get the resource ID for policy definition.

{
  "$schema": "https://schema.management.azure.com/schemas/2019-08-01/managementGroupDeploymentTemplate.json#",
  "contentVersion": "1.0.0.0",
  "parameters": {
    "targetMG": {
      "type": "string",
      "metadata": {
        "description": "Target Management Group"
      }
    },
    "allowedLocations": {
      "type": "array",
      "defaultValue": [
        "chinaeast",
        "chinanorth",
        "chinanorth2"
      ],
      "metadata": {
        "description": "An array of the allowed locations, all other locations will be denied by the created policy."
      }
    }
  },
  "variables": {
    "mgScope": "[tenantResourceId('Microsoft.Management/managementGroups', parameters('targetMG'))]",
    "policyDefinitionName": "LocationRestriction"
  },
  "resources": [
    {
      "type": "Microsoft.Authorization/policyDefinitions",
      "apiVersion": "2021-06-01",
      "name": "[variables('policyDefinitionName')]",
      "properties": {
        "policyType": "Custom",
        "mode": "All",
        "parameters": {},
        "policyRule": {
          "if": {
            "not": {
              "field": "location",
              "in": "[parameters('allowedLocations')]"
            }
          },
          "then": {
            "effect": "deny"
          }
        }
      }
    },
    "location_lock": {
      "type": "Microsoft.Authorization/policyAssignments",
      "apiVersion": "2022-06-01",
      "name": "location-lock",
      "properties": {
        "scope": "[variables('mgScope')]",
        "policyDefinitionId": "[managementGroupResourceId('Microsoft.Authorization/policyDefinitions', variables('policyDefinitionName'))]"
      },
      "dependsOn": [
        "[format('Microsoft.Authorization/policyDefinitions/{0}', variables('policyDefinitionName'))]"
      ]
    }
  ]
}

tenantResourceId

tenantResourceId(resourceType, resourceName1, [resourceName2], ...)

Returns the unique identifier for a resource deployed at the tenant level.

In Bicep, use the tenantResourceId function.

Parameters

Parameter Required Type Description
resourceType Yes string Type of resource including resource provider namespace.
resourceName1 Yes string Name of resource.
resourceName2 No string Next resource name segment, if needed.

Continue adding resource names as parameters when the resource type includes more segments.

Return value

The identifier is returned in the following format:

/providers/{resourceProviderNamespace}/{resourceType}/{resourceName}

Remarks

You use this function to get the resource ID for a resource that is deployed to the tenant. The returned ID differs from the values returned by other resource ID functions by not including resource group or subscription values.

tenantResourceId example

Built-in policy definitions are tenant level resources. To deploy a policy assignment that references a built-in policy definition, use the tenantResourceId function.

{
  "$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
  "contentVersion": "1.0.0.0",
  "parameters": {
    "policyDefinitionID": {
      "type": "string",
      "defaultValue": "0a914e76-4921-4c19-b460-a2d36003525a",
      "metadata": {
        "description": "Specifies the ID of the policy definition or policy set definition being assigned."
      }
    },
    "policyAssignmentName": {
      "type": "string",
      "defaultValue": "[guid(parameters('policyDefinitionID'), resourceGroup().name)]",
      "metadata": {
        "description": "Specifies the name of the policy assignment, can be used defined or an idempotent name as the defaultValue provides."
      }
    }
  },
  "resources": [
    {
      "type": "Microsoft.Authorization/policyAssignments",
      "name": "[parameters('policyAssignmentName')]",
      "apiVersion": "2022-06-01",
      "properties": {
        "scope": "[subscriptionResourceId('Microsoft.Resources/resourceGroups', resourceGroup().name)]",
        "policyDefinitionId": "[tenantResourceId('Microsoft.Authorization/policyDefinitions', parameters('policyDefinitionID'))]"
      }
    }
  ]
}

Next steps