GraphQLController

GraphQL Controllers act like a resolver, while also defining their schema. You define the operation input which must be a DTO declared inside the same module with the Controller.

It is also necessary to define the operation type of the controller, as a result defining the interaction of the controller with the GraphQL clients.

controller-graphql.bl

GraphQLController HelloWorldGQLController () {
  operation: GraphQL.Operations.Query;
  input: HelloWorldRequestDTO;

  execute (request): HelloWorldResponseDTO {
    const response = HelloWorldResponseDTO({
        message: 'Hello World!'
    })
    return this.ok(response);
  }
}

It is important that you return a value, either success or error, otherwise the operation will fail.

Operation type

OperationType	Description
GraphQL.Operations.Query	a read‐only fetch.
GraphQL.Operations.Mutation	a write followed by a fetch.
GraphQL.Operations.Subscription	a long‐lived request that fetches data in response to source events.

Return values and error-handling

OperationType	Description
this.ok(DTO)	regular response for success
this.clientError(message?: string)	UserInputError
this.unauthorized(message?: string)	AuthenticationError
this.forbidden(message?: string)	ForbiddenError
this.fail(error: Error | string)	ApolloError