@angular/core

FactoryProvider

interface

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']);