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FactoryProvider

配置此 Injector 以便调用 useFactory 函数返回一个值。

Configures the Injector to return a value by invoking a useFactory function.

      
      interface FactoryProvider extends FactorySansProvider {
  provide: any
  multi?: boolean

  // 继承自 core/FactorySansProvider
  useFactory: Function
  deps?: any[]
}
    

参见

属性

属性说明
provide: any

注入令牌。(通常是 TypeInjectionToken 的实例,但也可以是 any 实例)。

An injection token. (Typically an instance of Type or InjectionToken, but can be any).

multi?: boolean

如果为 true,则注入器返回实例数组。这对于允许多个提供者散布在多个文件中,以向某个公共令牌提供配置信息很有用。

When true, injector returns an array of instances. This is useful to allow multiple providers spread across many files to provide configuration information to a common token.

使用说明

      
      const Location = new InjectionToken('location');
const Hash = new InjectionToken('hash');

const injector = Injector.create({
  providers: [
    {provide: Location, useValue: 'https://angular.io/#someLocation'}, {
      provide: Hash,
      useFactory: (location: string) => location.split('#')[1],
      deps: [Location]
    }
  ]
});

expect(injector.get(Hash)).toEqual('someLocation');
    

Dependencies can also be marked as optional:

      
      const Location = new InjectionToken('location');
const Hash = new InjectionToken('hash');

const injector = Injector.create({
  providers: [{
    provide: Hash,
    useFactory: (location: string) => `Hash for: ${location}`,
    // use a nested array to define metadata for dependencies.
    deps: [[new Optional(), Location]]
  }]
});

expect(injector.get(Hash)).toEqual('Hash for: null');
    

Multi-value example

      
      const locale = new InjectionToken<string[]>('locale');
const injector = Injector.create({
  providers: [
    {provide: locale, multi: true, useValue: 'en'},
    {provide: locale, multi: true, useValue: 'sk'},
  ]
});

const locales: string[] = injector.get(locale);
expect(locales).toEqual(['en', 'sk']);