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({
    class: 'UserAuthInput',
    type: GraphQLString,
  })
  emailAddress: string;

  @gqlField({
    class: 'UserAuthInput',
    type: GraphQLString,
  })
  password: string; 

  constructor(emailAddress: string, password: string) {
    this.emailAddress = emailAddress;
    this.password = password;
  }
}

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

  constructor(viewerID: ID) {
    this.viewerID = viewerID;
  }
}

export class AuthResolver {
  @gqlMutation({ 
    class: "AuthResolver",
    name: "userAuth", 
    type: UserAuthPayload,
    async: true,
    args: [
      gqlContextType(),
      {
        name: "input",
        type: "UserAuthInput",
      },
    ]
  })
  async userAuth(
    context: RequestContext,
    input: UserAuthInput,
  ): Promise<UserAuthPayload> {
    return new UserAuthPayload("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
• gqlInputObjectType
• gqlField
• gqlObjectType
• gqlContextType

gqlMutation

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

Accepts the following options which overlap with gqlField:

• class for the name of the class the function is defined in.
• name for the name of the GraphQL field
• description of the field
• type: type returned by the field