intro.md

Introduction

Effects

In @ngrx/effects, effects are sources of actions. You use the @Effect() decorator to hint which observables on a service are action sources, and @ngrx/effects automatically merges your action streams letting you subscribe them to store.

To help you compose new action sources, @ngrx/effects exports an Actions observable service that emits every action dispatched in your application.

Example

1. Create an AuthEffects service that describes a source of login actions:

import { Injectable } from '@angular/core';
import { Http } from '@angular/http';
import { Actions, Effect } from '@ngrx/effects';
import { Observable } from 'rxjs/Observable';

@Injectable()
export class AuthEffects {
  constructor(
    private http: Http,
    private actions$: Actions
  ) { }

  @Effect() login$ = this.actions$
      // Listen for the 'LOGIN' action
      .ofType('LOGIN')
      // Map the payload into JSON to use as the request body
      .map(action => JSON.stringify(action.payload))
      .switchMap(payload => this.http.post('/auth', payload)
        // If successful, dispatch success action with result
        .map(res => ({ type: 'LOGIN_SUCCESS', payload: res.json() }))
        // If request fails, dispatch failed action
        .catch(() => Observable.of({ type: 'LOGIN_FAILED' }))
      );
}

2. Provide your service via EffectsModule.run to automatically start your effect:

import { EffectsModule } from '@ngrx/effects';
import { AuthEffects } from './effects/auth';

@NgModule({
  imports: [
    EffectsModule.run(AuthEffects)
  ]
})
export class AppModule { }

Note: For effects that depend on the application to be bootstrapped (i.e. effects that depend on the Router) use EffectsModule.runAfterBootstrap. Be aware that runAfterBootstrap will only work in the root module.

SystemJS Configuration

@ngrx/effects is published with a UMD bundle. Map @ngrx/effects imports to the bundle:

System.config({
  map: {
    '@ngrx/effects': 'npm:@ngrx/effects/bundles/effects.umd.js'
  }
})