Vmeda.Online/src/classes/singletons-factory.ts

77 lines
2.4 KiB
TypeScript

// (C) Copyright 2015 Moodle Pty Ltd.
//
// 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.
import { Injector, Type } from '@angular/core';
/**
* Stub class used to type anonymous classes created in CoreSingletonsFactory#makeSingleton method.
*/
class CoreSingleton {}
/**
* Token that can be used to resolve instances from the injector.
*/
export type CoreInjectionToken<Service> = Type<Service> | Type<any> | string;
/**
* Singleton class created using the factory.
*/
export type CoreSingletonClass<Service> = typeof CoreSingleton & { instance: Service };
/**
* Factory used to create CoreSingleton classes that get instances from an injector.
*/
export class CoreSingletonsFactory {
/**
* Angular injector used to resolve singleton instances.
*/
private injector: Injector;
/**
* Set the injector that will be used to resolve instances in the singletons created with this factory.
*
* @param injector Injector.
*/
setInjector(injector: Injector): void {
this.injector = injector;
}
/**
* Make a singleton that will hold an instance resolved from the factory injector.
*
* @param injectionToken Injection token used to resolve the singleton instance. This is usually the service class if the
* provider was defined using a class or the string used in the `provide` key if it was defined using an object.
*/
makeSingleton<Service>(injectionToken: CoreInjectionToken<Service>): CoreSingletonClass<Service> {
// tslint:disable: no-this-assignment
const factory = this;
return class {
private static _instance: Service;
static get instance(): Service {
// Initialize instances lazily.
if (!this._instance) {
this._instance = factory.injector.get(injectionToken);
}
return this._instance;
}
};
}
}