using_redux_with_components.md

Using Redux with Components

We will use the select pattern from Ng2-Redux to bind our components to the store. To demonstrate how this works, let's take a look at a small example with a counter component.

Counter Example

Let's start by building out a counter component. The component will be responsible for keeping track of how many times it was clicked and displaying that amount.

app/components/counter-component.ts

import { Component } from '@angular/core';
import { select } from 'ng2-redux';
import { CounterActions } from '../actions/counter-actions';

@Component({
  selector: 'counter',
  providers: [ CounterActions ],
  template: `
  <p>
    Clicked: {{ counter$ | async }} times
    <button (click)="actions.increment()">+</button>
    <button (click)="actions.decrement()">-</button>
    <button (click)="actions.incrementIfOdd()">Increment if odd</button>
    <button (click)="actions.incrementAsync()">Increment async</button>
  </p>
  `
})
export class Counter {
  @select() counter$: Observable<number>;

  constructor(private actions: CounterActions) {}
}

View Example

The template syntax should be familiar by now, displaying a Observable counter with the async pipe and handling some click events.

In this case, the click events are bound to expressions that call our action creators from the CounterActions ActionCreatorService.

Let's take a look at the use of @select.

@select is a feature of Ng2-Redux which is designed to help you attach your store's state to your components in a declarative way. You can attach it to a property of your component class and Ng2-Redux will create an Observable and bind it to that property for you.

In this case, @select has no parameters, so Ng2-Redux will look for a store property with the same name as the class variable. It omits the trailing $ since that's simply a naming convention for Observables.

So now, any time store.counter is updated by a reducer, counter$ will receive the new value and | async will update it in the template.

Note that @select supports a wide range of arguments to allow you to select portions of your Redux store with a great deal of flexibility. See the Ng2-Redux docs for more details.

The Ng2-Redux "select pattern" style differs a bit from the "connect" style used by react-redux; however by using Angular 2's DI and TypeScript's decorators, we can have a nicely declarative binding where most of the work is done in the template. We also get the power of Observables and OnPush change detection for better performance.

Either way, we still benefit the Redux fundamentals of reducers and one-way data-flow.