Example: Mutation helper

task_mutations.ts

export function heartTask(attr: {
  datastore: DatastoreService;
  // Thin interfaces for the User/Task model which utilize TypeScript's
  // structural typing, but the type aliases are omitted for brevity.
  user: UserBase;
  task: TaskBase;
}) {
  attr.datastore.runInBatch(() => {
    // 1. Optimistically create the object representing the heart.
    var heartRequest = new HeartCreateRequest({
      target: attr.task.dbObjectId(),
      user: attr.user.dbObjectId()
    });
    var heartId = attr.datastore.createDbObject(heartRequest);

    // 2. Send server request to update the database.
    attr.services.datastore.requestServerChange(
      “post”, “/task_heart”, {
        // server will create an identical object with the same ID.
        global_id: heartId,
        task: task.dbObjectId(),
        user: attr.user.dbObjectId()
      }
    );
  });
});