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API > @angular/core

Injector

Concrete injectors implement this interface.

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      abstract class Injector {
  static THROW_IF_NOT_FOUND: _THROW_IF_NOT_FOUND
  static NULL: Injector
  static ngInjectableDef: ɵɵdefineInjectable({...})
  static create(options: StaticProvider[] | { providers: StaticProvider[]; parent?: Injector; name?: string; }, parent?: Injector): Injector
  abstract get<T>(token: Type<T> | InjectionToken<T>, notFoundValue?: T, flags?: InjectFlags): T
}

Subclasses

Description

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

Static properties

Property Description
static THROW_IF_NOT_FOUND: _THROW_IF_NOT_FOUND
static NULL: Injector
static ngInjectableDef: ɵɵdefineInjectable({ providedIn: 'any' as any, factory: () => ɵɵinject(INJECTOR) })

Static methods

create()

Create a new Injector which is configure using StaticProviders.
static create(providers: StaticProvider[], parent?: Injector): Injector
      
      static create(providers: StaticProvider[], parent?: Injector): Injector

Deprecated from v5 use the new signature Injector.create(options)

Parameters
providers StaticProvider[]
parent Injector

Optional. Default is undefined.
Returns

Injector
static create(options: { providers: StaticProvider[]; parent?: Injector; name?: string; }): Injector
      
      static create(options: { providers: StaticProvider[]; parent?: Injector; name?: string; }): Injector
Parameters
options object
Returns

Injector

Usage Notes

Example
class Square { name = 'square'; } const injector = Injector.create({providers: [{provide: Square, deps: []}]}); const shape: Square = injector.get(Square); expect(shape.name).toEqual('square'); expect(shape instanceof Square).toBe(true); 
      
      class Square {
  name = 'square';
}

const injector = Injector.create({providers: [{provide: Square, deps: []}]});

const shape: Square = injector.get(Square);
expect(shape.name).toEqual('square');
expect(shape instanceof Square).toBe(true);

Methods

get()

Retrieves an instance from the injector based on the provided token.
abstract get<T>(token: Type<T> | InjectionToken<T>, notFoundValue?: T, flags?: InjectFlags): T
      
      abstract get<T>(token: Type<T> | InjectionToken<T>, notFoundValue?: T, flags?: InjectFlags): T
Parameters
token Type | InjectionToken
notFoundValue T

Optional. Default is undefined.
flags InjectFlags

Optional. Default is undefined.
Returns

T: The instance from the injector if defined, otherwise the notFoundValue.

Throws

Error When the notFoundValue is undefined or Injector.THROW_IF_NOT_FOUND.
abstract get(token: any, notFoundValue?: any): any
      
      abstract get(token: any, notFoundValue?: any): any

Deprecated from v4.0.0 use Type or InjectionToken

Parameters
token any
notFoundValue any

Optional. Default is undefined.
Returns

any

Usage notes

Example

const injector: Injector = Injector.create({providers: [{provide: 'validToken', useValue: 'Value'}]}); expect(injector.get('validToken')).toEqual('Value'); expect(() => injector.get('invalidToken')).toThrowError(); expect(injector.get('invalidToken', 'notFound')).toEqual('notFound'); 
      
      const injector: Injector =
    Injector.create({providers: [{provide: 'validToken', useValue: 'Value'}]});
expect(injector.get('validToken')).toEqual('Value');
expect(() => injector.get('invalidToken')).toThrowError();
expect(injector.get('invalidToken', 'notFound')).toEqual('notFound');

Injector returns itself when given Injector as a token:

const injector = Injector.create({providers: []}); expect(injector.get(Injector)).toBe(injector); 
      
      const injector = Injector.create({providers: []});
expect(injector.get(Injector)).toBe(injector);