@angular/core

ClassProvider

interface

stable

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

API

    
      interface ClassProvider extends ClassSansProvider {}

provide

any

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

multi

boolean | undefined

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.

useClass

Type<any>

Class to instantiate for the 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']);