$toObjectId

APPLIES TO: MongoDB vCore

The $toObject operator converts a specified string value into an ObjectId.

Syntax

The syntax for the $toObject operator is:

{ "$toObject": <expression> }

Parameters

Parameter Description
expression The specified string value to convert into an ObjectId

Examples

Example 1: Convert the first 24 alphanumeric characters in the _id field into an ObjectId value

This query removes all occurrences of the "-" character and takes the first twenty four characters in the _id field and converts the result into an ObjectId. The ObjectId operator must strictly have a string of length twenty four with only alphanumeric characters.

db.stores.aggregate([
{
    "$match": {
        "_id": "b0107631-9370-4acd-aafa-8ac3511e623d"
    }
},
{
    "$project": {
        "idAsObjectId": {
            "$toObjectId": {
                "$substr": [
                    {
                        "$replaceAll": {
                            "input": "$_id",
                            "find": "-",
                            "replacement": ""
                        }
                    }, 0, 24]
            }
        }
    }
}])

This results in the following output:

{
    "_id": "b0107631-9370-4acd-aafa-8ac3511e623d",
    "idAsObjectId": "ObjectId('b010763193704acdaafa8ac3')"
}

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