Angular

What it does

Configures the Injector to return an instance of useClass for a token.

How to use

@Injectable() class MyService {} const provider: ClassProvider = {provide: 'someToken', useClass: MyService};

Interface Overview

interface ClassProvider {

provide : any

useClass : Type<any>

multi : boolean

}

Interface Description

For more details, see the Dependency Injection Guide.

Example

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));

Interface Details

provide : any

An injection token. (Typically an instance of Type or OpaqueToken, but can be any).

useClass : Type<any>

Class to instantiate for the token.

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 @angular/core/index, defined in @angular/core/src/di/provider.ts