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Custom Mutations

As a product gets more complicated, the need to eventually add custom mutations to the schema arises. This shows how to do so.

Auth Example​

A common thing for a lot of applications is to implement authentication to log the user in. This shows a possible way to implement it:

src/graphql/mutations/auth.ts
@gqlInputObjectType()
export class UserAuthInput {
  @gqlField()
  emailAddress: string; 
  @gqlField()
  password: string; 
}

@gqlObjectType()
export class UserAuthPayload {
  @gqlField({ type: GraphQLID })
  viewerID: ID; 
}

export class AuthResolver {
  @gqlMutation({ name: "userAuth", type: UserAuthPayload })
  async userAuth(

    @gqlContextType() context: RequestContext,
    @gqlArg("input") input: UserAuthInput,

  ): Promise<UserAuthPayload> {

    return {viewerID : "1"};

  }
}

This updates the GraphQL schema as follows:

src/graphql/generated/schema.gql

type Mutation {
  userAuth(input: UserAuthInput!): UserAuthPayload!
}

type UserAuthPayload {
  viewerID: ID!
}

input UserAuthInput {
  emailAddress: String!
  password: String!
}

Here's what's happening here:

  • This adds a new input type UserAuthInput to the GraphQLSchema represented by the class UserAuthInput.
  • UserAuthInput object has 2 fields:
    • emailAddress of type String
    • password of type String
  • This adds a new object type UserAuthPayload to the GraphQLSchema represented by the class UserAuthPayload
  • UserAuthPayload object has 1 field:
    • viewerID of type ID
  • New field userAuth added to Mutation Type which takes UserAuthInput input and returns UserAuthPayload.

This uses the following concepts to implement this:

gqlMutation​

This adds a new field to the GraphQL Mutation type. See example usage above.

Accepts the following options which overlap with gqlField:

  • name for the name of the GraphQL field
  • description of the field
  • type: type returned by the field

gqlInputObjectType​

Adds a new input object to the schema. See example usage above.

Options:

name​

Name of the input object. If not specified, defaults to the name of the class.

description​

Description nof the input object. Will be added to the Schema and exposed in tools like GraphiQL or Playground.

gqlObjectType​

Adds a new object to the schema. See example usage above.

Options:

name​

Name of the object. If not specified, defaults to the name of the class

description​

Description nof the object. Will be added to the Schema and exposed in tools like GraphiQL or Playground.