FactoryProvider
Configures the Injector to return a value by invoking a useFactory function.
interface FactoryProvider extends FactorySansProvider {
provide: any
multi?: boolean
}
说明
For more details, see the "Dependency Injection Guide".
属性
| 属性 | 说明 |
|---|---|
provide: any | An injection token. (Typically an instance of |
multi?: boolean | If true, then 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
Example
- const Location = new InjectionToken('location');
- const Hash = new InjectionToken('hash');
-
- const injector = Injector.create([
- {provide: Location, useValue: 'http://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([{
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([
{provide: locale, multi: true, useValue: 'en'},
{provide: locale, multi: true, useValue: 'sk'},
]);
const locales: string[] = injector.get(locale);
expect(locales).toEqual(['en', 'sk']);
