@angular/core

FactoryProvider

interface

stable

Configures the Injector to return a value by invoking a useFactory function.

API

  interface FactoryProvider extends FactorySansProvider {}

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.

useFactory

Function

A function to invoke to create a value for this token. The function is invoked with resolved values of tokens in the deps field.

deps

any[] | undefined

A list of tokens to be resolved by the injector. The list of values is then used as arguments to the useFactory function.

Usage Notes

const Location = new InjectionToken('location'); const Hash = new InjectionToken('hash'); const injector = Injector.create({ providers: [ {provide: Location, useValue: 'https://angular.io/#someLocation'}, { provide: Hash, useFactory: (location: string) => location.split('#')[1], deps: [Location], }, ], }); expect(injector.get(Hash)).toEqual('someLocation');

Dependencies can also be marked as optional:

const Location = new InjectionToken('location'); const Hash = new InjectionToken('hash'); const injector = Injector.create({ providers: [ { provide: Hash, useFactory: (location: string) => `Hash for: ${location}`, // use a nested array to define metadata for dependencies. deps: [[new Optional(), Location]], }, ], }); expect(injector.get(Hash)).toEqual('Hash for: null');

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']);