Injector - Angular

Concrete injectors implement this interface. Injectors are configured with providers that associate dependencies of various types with injection tokens.

API

abstract class Injector {
  abstract get<T>(token: ProviderToken<T>, notFoundValue: undefined, options: InjectOptions & { optional?: false | undefined; }): T;
  abstract get<T>(token: ProviderToken<T>, notFoundValue: null | undefined, options: InjectOptions): T | null;
  abstract get<T>(token: ProviderToken<T>, notFoundValue?: T | undefined, options?: InjectOptions | undefined): T;
  abstract get<T>(token: string | ProviderToken<T>, notFoundValue?: any): any;
  static THROW_IF_NOT_FOUND: {};
  static NULL: Injector;
  static create(providers: StaticProvider[], parent?: Injector | undefined): Injector;
  static create(options: { providers: (any[] | TypeProvider | ValueProvider | ClassProvider | ConstructorProvider | ExistingProvider | FactoryProvider | StaticClassProvider)[]; parent?: Injector | undefined; name?: string | undefined; }): DestroyableInjector;
}

get

4 overloads

Retrieves an instance from the injector based on the provided token.

@paramtokenProviderToken<T>

@paramnotFoundValueundefined

@paramoptionsInjectOptions & { optional?: false | undefined; }

@returnsT

Retrieves an instance from the injector based on the provided token.

@paramtokenProviderToken<T>

@paramnotFoundValuenull | undefined

@paramoptionsInjectOptions

@returnsT | null

Retrieves an instance from the injector based on the provided token.

@paramtokenProviderToken<T>

@paramnotFoundValueT | undefined

@paramoptionsInjectOptions | undefined

@returnsT

@deprecated

from v4.0.0 use ProviderToken

@paramtokenstring | ProviderToken<T>

@paramnotFoundValueany

@returnsany

THROW_IF_NOT_FOUND

{}

NULL

Injector

create

2 overloads

@deprecated

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

@paramprovidersStaticProvider[]

@paramparentInjector | undefined

@returnsInjector

Creates a new injector instance that provides one or more dependencies, according to a given type or types of StaticProvider.

@paramoptions

{ providers: (any[] | TypeProvider | ValueProvider | ClassProvider | ConstructorProvider | ExistingProvider | FactoryProvider | StaticClassProvider)[]; parent?: Injector | undefined; name?: string | undefined; }

An object with the following properties:

providers: An array of providers of the StaticProvider type.
parent: (optional) A parent injector.
name: (optional) A developer-defined identifying name for the new injector.

@returnsDestroyableInjector

Usage Notes

The following example creates a service injector instance.

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);

Usage 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');

Injector returns itself when given Injector as a token:

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