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Injector

class

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

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

Subclasses

See also

Provided in

  • 'any'

Static properties

Property Description
static THROW_IF_NOT_FOUND: THROW_IF_NOT_FOUND
static NULL: Injector

Static methods

create()

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

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

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

Parameters
options object

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.
Returns

Injector: The new injector instance.

Methods

get()

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

abstract get<T>(token: ProviderToken<T>, notFoundValue?: T, flags?: InjectFlags): T

Parameters
token ProviderToken
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

Deprecated from v4.0.0 use ProviderToken

Parameters
token any
notFoundValue any

Optional. Default is undefined.
Returns

any

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);

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Licensed under the Creative Commons Attribution License 4.0.
https://v12.angular.io/api/core/Injector