Projection - Operation Add Type Attribute

Artikkel
02/16/2022

Overview

AddTypeAttribute is a projection operation that adds a user-specified type attribute to the final resolved entity. It is generally used after a CombineAttributes operation to create a type attribute that indicates the type that matches one of the entities from a polymorphic source, but can also be used by itself. Think of it like the $type property in a JSON object.

For example: We have an Account entity with the attribute "accountId" and a Contact entity with the attribute "contactId". Using CombineAttributes, we merge "accountId" and "contactId" into "customerId". We can then use AddTypeAttribute to create a "customerType" type attribute that is used to indicate whether "customerId" is an Account or a Contact type.

Because of this, the created type attribute is often an "entityName" data type. It will also have the trait is.linkedEntity.name.

Note: you can access the API reference for this operation on this link.

Examples

The examples below refer to the ContactKinds entity as defined here.

{
    "entityName": "ContactKinds",
    "hasAttributes": [
        {
            "name": "emailKind",
            "entity": "Email"
        },
        { 
            "name": "phoneKind", 
            "entity": "Phone"
        },
        {
            "name": "socialKind",
            "entity": "Social"
        }
    ]
}

Email	Phone	Social
emailId	phoneId	socialId
address	number	account
isPrimary	isPrimary	isPrimary

Using the AddTypeAttribute operation on an entity attribute

If we have an entity attribute, we can use AddTypeAttribute to add a type attribute. We can have an entity, Customer, that contains the following entity attribute definition (called contactAt) with a CombineAttributes operation (using ContactKinds as the source) that merges "emailId", "phoneId", and "socialId" into "contactId":

{
    "name": "contactAt",
    "isPolymorphicSource": true,
    "entity": {
        "operations": [
            {
                "$type": "addTypeAttribute",
                "typeAttribute": {
                    "name": "contactType",
                    "dataType": "entityName",
                    "appliedTraits": []
                }
            }
        ],
        "source": {
            "operations": [
                {
                    "$type": "combineAttributes",
                    "select": ["emailId", "phoneId", "socialId"],
                    "mergeInto": {
                        "name": "contactId",
                        "dataType": "entityId"
                    }
                }
            ],
            "source": "ContactKinds"
        }
    }
}

The resulting resolved contactAt entity typed attribute is:

contactAt
address
isPrimary
number
account
contactId
contactType

Using the AddTypeAttribute operation when extending an entity

If we have an entity that extends another entity, we can use AddTypeAttribute to add a type attribute.

Given the entity, Customer, that extends from the ContactKinds entity:

{
    "entityName": "Customer",
    "extendsEntity": {
        "operations": [
            {
                "$type": "addTypeAttribute",
                "typeAttribute": {
                    "name": "contactType",
                    "dataType": "entityName",
                    "appliedTraits": []
                }
            }
        ],
        "source": {
            "operations": [
                {
                    "$type": "combineAttributes",
                    "select": [ "emailId", "phoneId", "socialId" ],
                    "mergeInto": {
                        "name": "contactId",
                        "dataType": "entityId"
                    }
                }
            ],
            "source": "ContactKinds"
        }
    },
    "hasAttributes": []
}

The resulting resolved Customer entity is:

Customer
address
isPrimary
number
account
contactId
contactType

Using the AddTypeAttribute operation by itself

{
    "name": "contactAt",
    "entity": {
        "source": "ContactKinds",
        "operations": [
            {
                "$type": "addTypeAttribute",
                "typeAttribute": {
                    "name": "someType",
                    "dataType": "entityName"
                }
            }
        ]
    }
}