@lumino/coreutils/src/promise.ts

Lumino Core Utilities

// Copyright (c) Jupyter Development Team.
// Distributed under the terms of the Modified BSD License.
/*-----------------------------------------------------------------------------
| Copyright (c) 2014-2017, PhosphorJS Contributors
|
| Distributed under the terms of the BSD 3-Clause License.
|
| The full license is in the file LICENSE, distributed with this software.
|----------------------------------------------------------------------------*/

/**
 * A class which wraps a promise into a delegate object.
 *
 * #### Notes
 * This class is useful when the logic to resolve or reject a promise
 * cannot be defined at the point where the promise is created.
 */
export class PromiseDelegate<T> {
  /**
   * Construct a new promise delegate.
   */
  constructor() {
    this.promise = new Promise<T>((resolve, reject) => {
      this._resolve = resolve;
      this._reject = reject;
    });
  }

  /**
   * The promise wrapped by the delegate.
   */
  readonly promise: Promise<T>;

  /**
   * Resolve the wrapped promise with the given value.
   *
   * @param value - The value to use for resolving the promise.
   */
  resolve(value: T | PromiseLike<T>): void {
    let resolve = this._resolve;
    resolve(value);
  }

  /**
   * Reject the wrapped promise with the given value.
   *
   * @reason - The reason for rejecting the promise.
   */
  reject(reason: unknown): void {
    let reject = this._reject;
    reject(reason);
  }

  private _resolve: (value: T | PromiseLike<T>) => void;
  private _reject: (reason: any) => void;
}