| // Copyright 2013 The Closure Library Authors. All Rights Reserved. |
| // |
| // Licensed under the Apache License, Version 2.0 (the "License"); |
| // you may not use this file except in compliance with the License. |
| // You may obtain a copy of the License at |
| // |
| // http://www.apache.org/licenses/LICENSE-2.0 |
| // |
| // Unless required by applicable law or agreed to in writing, software |
| // distributed under the License is distributed on an "AS-IS" BASIS, |
| // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| // See the License for the specific language governing permissions and |
| // limitations under the License. |
| |
| goog.provide('goog.Thenable'); |
| |
| |
| |
| /** |
| * Provides a more strict interface for Thenables in terms of |
| * http://promisesaplus.com for interop with {@see goog.Promise}. |
| * |
| * @interface |
| * @extends {IThenable<TYPE>} |
| * @template TYPE |
| */ |
| goog.Thenable = function() {}; |
| |
| |
| /** |
| * Adds callbacks that will operate on the result of the Thenable, returning a |
| * new child Promise. |
| * |
| * If the Thenable is fulfilled, the {@code onFulfilled} callback will be |
| * invoked with the fulfillment value as argument, and the child Promise will |
| * be fulfilled with the return value of the callback. If the callback throws |
| * an exception, the child Promise will be rejected with the thrown value |
| * instead. |
| * |
| * If the Thenable is rejected, the {@code onRejected} callback will be invoked |
| * with the rejection reason as argument, and the child Promise will be rejected |
| * with the return value of the callback or thrown value. |
| * |
| * @param {?(function(this:THIS, TYPE): |
| * (RESULT|IThenable<RESULT>|Thenable))=} opt_onFulfilled A |
| * function that will be invoked with the fulfillment value if the Promise |
| * is fullfilled. |
| * @param {?(function(this:THIS, *): *)=} opt_onRejected A function that will |
| * be invoked with the rejection reason if the Promise is rejected. |
| * @param {THIS=} opt_context An optional context object that will be the |
| * execution context for the callbacks. By default, functions are executed |
| * with the default this. |
| * @return {!goog.Promise<RESULT>} A new Promise that will receive the result |
| * of the fulfillment or rejection callback. |
| * @template RESULT,THIS |
| */ |
| goog.Thenable.prototype.then = function(opt_onFulfilled, opt_onRejected, |
| opt_context) {}; |
| |
| |
| /** |
| * An expando property to indicate that an object implements |
| * {@code goog.Thenable}. |
| * |
| * {@see addImplementation}. |
| * |
| * @const |
| */ |
| goog.Thenable.IMPLEMENTED_BY_PROP = '$goog_Thenable'; |
| |
| |
| /** |
| * Marks a given class (constructor) as an implementation of Thenable, so |
| * that we can query that fact at runtime. The class must have already |
| * implemented the interface. |
| * Exports a 'then' method on the constructor prototype, so that the objects |
| * also implement the extern {@see goog.Thenable} interface for interop with |
| * other Promise implementations. |
| * @param {function(new:goog.Thenable,...?)} ctor The class constructor. The |
| * corresponding class must have already implemented the interface. |
| */ |
| goog.Thenable.addImplementation = function(ctor) { |
| goog.exportProperty(ctor.prototype, 'then', ctor.prototype.then); |
| if (COMPILED) { |
| ctor.prototype[goog.Thenable.IMPLEMENTED_BY_PROP] = true; |
| } else { |
| // Avoids dictionary access in uncompiled mode. |
| ctor.prototype.$goog_Thenable = true; |
| } |
| }; |
| |
| |
| /** |
| * @param {*} object |
| * @return {boolean} Whether a given instance implements {@code goog.Thenable}. |
| * The class/superclass of the instance must call {@code addImplementation}. |
| */ |
| goog.Thenable.isImplementedBy = function(object) { |
| if (!object) { |
| return false; |
| } |
| try { |
| if (COMPILED) { |
| return !!object[goog.Thenable.IMPLEMENTED_BY_PROP]; |
| } |
| return !!object.$goog_Thenable; |
| } catch (e) { |
| // Property access seems to be forbidden. |
| return false; |
| } |
| }; |