ExistingProvider
Configures the Injector to return a value of another useExisting token.
interface ExistingProvider extends ExistingSansProvider {
provide: any
multi?: boolean
// 继承自 core/ExistingSansProvider
useExisting: any
}
参见
属性
| 属性 | 说明 |
|---|---|
provide: any | An injection token. Typically an instance of |
multi?: boolean | 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
class Greeting {
salutation = 'Hello';
}
class FormalGreeting extends Greeting {
salutation = 'Greetings';
}
const injector = Injector.create([
{provide: FormalGreeting, deps: []}, {provide: Greeting, useExisting: FormalGreeting}
]);
expect(injector.get(Greeting).salutation).toEqual('Greetings');
expect(injector.get(FormalGreeting).salutation).toEqual('Greetings');
expect(injector.get(FormalGreeting)).toBe(injector.get(Greeting));
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']);
