Relay Input Object Mutations Specification

Relay’s support for mutations relies on the GraphQL server exposing mutation fields in a standardized way. These mutations accept and emit a identifier string, which allows Relay to track mutations and responses.

All mutations may include in their input a clientMutationId string, which is then returned as part of the object returned by the mutation field.

An example of this is the following query:

mutation M {
  updateStatus(input: $input) {
    clientMutationId
    status {
      text
    }
  }
}

where the provided parameters are:

{
  "input": {
    "clientMutationId": "549b5e7c-0516-4fc9-8944-125401211590",
    "text": "Hello World!"
  }
}

and the response is:

{
  "updateStatus": {
    "clientMutationId": "549b5e7c-0516-4fc9-8944-125401211590",
    "status": {
      "text": "Hello World!"
    }
  }
}

This section of the spec describes the formal requirements around mutations.

Contents
  1. 1Mutation inputs
  2. 2Mutation fields
  3. 3Introspection

1Mutation inputs

In particular, all mutations must expose exactly one argument, named input. This argument’s type must be a NON_NULL wrapper around an INPUT_OBJECT. That input object type may contain an argument named clientMutationId. If provided, that argument must be a String. That argument may be non‐null.

Clients may use whatever identifier they see fit for their clientMutationIds; Version 4 UUIDs are a reasonable choice.

2Mutation fields

The return type of any mutation field must be an object. That object may contain a field named clientMutationId which is a String. If input clientMutationId is non‐null, then mutation clientMutationId must also be non‐null. The value of this field must be the value of the clientMutationId input argument defined above.

3Introspection

A server that correctly implements the above requirement will accept the following introspection query, and return a response that contains the provided response.

{
  __schema {
    mutationType {
      fields {
        type {
          kind
          fields {
            name
            type {
              kind
              ofType {
                name
                kind
              }
            }
          }
        }
        args {
          name
          type {
            kind
            ofType {
              kind
              inputFields {
                name
                type {
                  kind
                  ofType {
                    name
                    kind
                  }
                }
              }
            }
          }
        }
      }
    }
  }
}

yields

{
  "__schema": {
    "mutationType": {
      "fields": [
        // May contain many instances of this
        {
          "type": {
            "kind": "OBJECT",
            "fields": [
              // May contain more fields here.
              {
                "name": "clientMutationId",
                // May also be NON_NULL, must match args
                "type": {
                  "name": "String",
                  "kind": "SCALAR"
                }
              }
            ]
          },
          "args": [
            {
              "name": "input",
              "type": {
                "kind": "NON_NULL",
                "ofType": {
                  "kind": "INPUT_OBJECT",
                  "inputFields": [
                    // May contain more fields here
                    {
                      "name": "clientMutationId",
                      // May also be NON_NULL, must match payload
                      "type": {
                        "name": "String",
                        "kind": "SCALAR"
                      }
                    }
                  ]
                }
              }
            }
          ]
        }
      ]
    }
  }
}
  1. 1Mutation inputs
  2. 2Mutation fields
  3. 3Introspection