What it does
Configures the Injector to return a value of another useExisting token.
How to use
const provider: ExistingProvider = {provide: 'someToken', useExisting: 'someOtherToken'};
Interface Overview
interface ExistingProvider {}
Interface Description
For more details, see the Dependency Injection Guide.
Example
class Greeting {
salutation = 'Hello';
}
class FormalGreeting extends Greeting {
salutation = 'Greetings';
}
const injector = ReflectiveInjector.resolveAndCreate(
[FormalGreeting, {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));
Interface Details
provide : any
An injection token. (Typically an instance of Type or InjectionToken, but can be any).
useExisting : any
Existing token to return. (equivalent to injector.get(useExisting))
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.
const injector = ReflectiveInjector.resolveAndCreate([
{provide: 'local', multi: true, useValue: 'en'},
{provide: 'local', multi: true, useValue: 'sk'},
]);
const locales: string[] = injector.get('local');
expect(locales).toEqual(['en', 'sk']);
exported from core/index,
defined in core/src/di/provider.ts