ClassProvider
Configures the Injector to return an instance of useClass for a token.
interface ClassProvider extends ClassSansProvider {
provide: any
multi?: boolean
// 继承自 core/ClassSansProvider
useClass: Type<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
abstract class Shape {
name!: string;
}
class Square extends Shape {
name = 'square';
}
const injector = ReflectiveInjector.resolveAndCreate([{provide: Shape, useClass: Square}]);
const shape: Shape = injector.get(Shape);
expect(shape.name).toEqual('square');
expect(shape instanceof Square).toBe(true);
Note that following two providers are not equal:
class Greeting {
salutation = 'Hello';
}
class FormalGreeting extends Greeting {
salutation = 'Greetings';
}
const injector = ReflectiveInjector.resolveAndCreate(
[FormalGreeting, {provide: Greeting, useClass: FormalGreeting}]);
// The injector returns different instances.
// See: {provide: ?, useExisting: ?} if you want the same instance.
expect(injector.get(FormalGreeting)).not.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']);
