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@angular/corecode
ClassProvider
interface
stable
Configures the Injector to return an instance of useClass for a token.
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API
interface ClassProvider extends ClassSansProvider { provide: any; multi?: boolean | undefined; override useClass: Type<any>;}
multi
boolean | undefinedWhen 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.
Usage Notes
abstract class Shape {
name!: string;
}
class Square extends Shape {
override name = 'square';
}
const injector = Injector.create({providers: [{provide: Shape, useValue: new 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 {
override salutation = 'Greetings';
}
const injector = Injector.create({
providers: [
{provide: FormalGreeting, useClass: 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({
providers: [
{provide: locale, multi: true, useValue: 'en'},
{provide: locale, multi: true, useValue: 'sk'},
],
});
const locales: string[] = injector.get(locale);
expect(locales).toEqual(['en', 'sk']);Jump to details