ExistingProvider

interface

Configures the Injector to return a value of another useExisting token.

      
      interface ExistingProvider extends ExistingSansProvider {
  provide: any
  multi?: boolean
}

Description

For more details, see the "Dependency Injection Guide".

Properties

Property	Description
`provide: any`	An injection token. (Typically an instance of `Type` or `InjectionToken`, but can be `any`).
`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.

Usage notes

Example

      
      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']);