FactoryProvider

interface

npm Package	@angular/core
Module	import { FactoryProvider } from '@angular/core';
Source	core/src/di/provider.ts

Interface Overview

interface FactoryProvider { 
  provide: any
  useFactory: Function
  deps?: any[]
  multi?: boolean
}

How To Use

function serviceFactory() { ... }

const provider: FactoryProvider = {provide: 'someToken', useFactory: serviceFactory, deps: []};

Description

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

Example

const Location = new InjectionToken('location');
const Hash = new InjectionToken('hash');

const injector = Injector.create([
  {provide: Location, useValue: 'http://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([{
  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');

Members

provide: any

An injection token. (Typically an instance of Type or InjectionToken, but can be any).

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[]

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

multi?: boolean

If true, then 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.

Example

const locale = new InjectionToken<string[]>('locale');
const injector = Injector.create([
  {provide: locale, multi: true, useValue: 'en'},
  {provide: locale, multi: true, useValue: 'sk'},
]);

const locales: string[] = injector.get(locale);
expect(locales).toEqual(['en', 'sk']);