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ClassProvider

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

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      interface ClassProvider extends ClassSansProvider {
  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

abstract class Shape { // TODO(issue/24571): remove '!'. 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); 
      
      
  1. abstract class Shape {  // TODO(issue/24571): remove '!'.
  2.   name !: string;
  3. }
  4.  
  5. class Square extends Shape {
  6.   name = 'square';
  7. }
  8.  
  9. const injector = ReflectiveInjector.resolveAndCreate([{provide: Shape, useClass: Square}]);
  10.  
  11. const shape: Shape = injector.get(Shape);
  12. expect(shape.name).toEqual('square');
  13. 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)); 
      
      
  1. class Greeting {
  2.   salutation = 'Hello';
  3. }
  4.  
  5. class FormalGreeting extends Greeting {
  6.   salutation = 'Greetings';
  7. }
  8.  
  9. const injector = ReflectiveInjector.resolveAndCreate(
  10.     [FormalGreeting, {provide: Greeting, useClass: FormalGreeting}]);
  11.  
  12. // The injector returns different instances.
  13. // See: {provide: ?, useExisting: ?} if you want the same instance.
  14. expect(injector.get(FormalGreeting)).not.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']); 
      
      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']);