@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']);

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