Redux Decorators

A ridiculously good syntax for working with Redux using decorators in ES7 / TypeScript. Currently limited to Angular 2 but could potentially be used elsewhere.

Try a live example on plunkr

Installation

npm i redux-decorators

Example Usage (Angular 2)

app.reducer.ts

import {InitialState, Reducer} from 'redux-decorators';

@Slice('count', 0)
@Reducer('add', 'remove')
export class AppReducer {
    add(count) { return count + 1; }
    remove(count) { return count - 1; }
}

In the above example we create a new class that will hold our action reducers. We use the @Slice decorator to specify which slice these action reducers receive. We also specify 0 for the default value of count.

We then register two action reducers with the @Reducer('add', 'remove') decorator. Anytime an add or remove action is dispatched the corresponding method will be called on the AppReducer class, allowing the method to update the state for that particular action.

count.component.ts

import {Component} from 'angular2/core';
import {Store} from 'redux-decorators';

@Component({
    selector: 'counter',
    template: `
        <div>Count: {{count}}</div>
        <button (click)="dispatch('add')">Add</button>
        <button (click)="dispatch('remove')">Remove</button>
    `
})

@Store('count')
export class CounterComponent {}

In the above example we used the @Store() decorator to register the CounterComponent as a store observer. We also registered the count property with the store which means that any changes to the count property in the application state will be automatically pushed through to the count property of this component.

Notice also the dispatch() method in the template. This method is provided by the @Store() decorator and can be used to easily dispatch an action.

boot.ts

import {bootstrap} from 'angular2/platform/browser';
import {AppComponent} from './app.component';
import './app.reducer';

bootstrap(AppComponent);

In the above example we imported the app.reducer as a side-effect only module - that's all we need to do.

API

Decorators

@Slice(slice: string, initialState?: any)

The @Slice decorator is used to specify what slice of the state tree action reducers receive. This allows your action reducers to be passed the data for the slice that they manipulate. The @Slice decorator can also be passed the default value for the specified state slice as the second argument.

@Slice('count', 0)
@Reducer('increment')
class MyActionReducers {
  increment(count) { return count + 1; } // increment is passed the value of the count slice
}

In the above example we use the @Slice decorator to specify that the MyActionReducers class operates on the count slice of the state tree. We also used the second argument to specify that count should be initialised with a default value of 0.

Advanced Usage

@Slice can be used with classes and methods. This means a single class of action reducers can work against multiple slices of the state tree. However, this approach is not advised. Action reducer classes should operate on a single slice of the state tree.

@Slice('count', 0)
@Reducer('increment', 'addItem')
class MyActionReducers {
  increment(count) { return count + 1; } // Initial state is 0 for the count slice

  @Slice('items')
  addItem(items) { return [...items, item]; } // Initial state is [] for the items slice
}

Above we have extended the previous example and used the @Slice decorator to specify that the addItems reducer should receive the value of the items slice from the state tree. This is an example of a single class operating on multiple state slices.

@Reducer([actionReducer1, actionReducer2, ...])

The Reducer() decorator is used to identify a root reducer, however it can also be used as a convenience method for setting multiple action reducers in a single call.

The @Reducer() decorator registers a new root reducer if the class you are decorating contains a reducer method.

Root Reducer

@Reducer()
class MyRootReducer implements IReducer {
    reducer(state = initialState, action) {
       ...
    }
}

In the above example, the MyRootReducer class contains a reducer method, this means that this class will be registered as the root reducer - this will overwrite the default root reducer and prevent action reducers from working out of the box.

Action Reducers
We can mark individual methods as action reducers.

class MyReducers {
    @Reducer() add(state): { return { count: state.count + 1; } }
    @Reducer() remove(state): { return { count: state.count - 1; } }
}

Alternatively we can mark multiple methods at once using @Reducer():

@Reducer('add', 'remove')
class MyReducers {
    add(state): { return { count: state.count + 1; } }
    remove(state): { return { count: state.count - 1; } }
}

@Store([stateProp1, stateProp2, ...])

The @Store() decorator is used to identify a store component. A store component is automatically subscribed to the application store and receives registered state updates when the store is updated.

@Store()
class TodoListComponent {
   ...
}

You'll also need to declare which properties are updated by the application store. You can do that by explicitly decorating each property with the @State() decorator, or you can declare these properties when you declare the @Store() decorator:

@Store('todos')
class TodoListComponent {
   ...
}

In the above example we are declaring that the todos property of the TodoListComponent should be automatically updated whenever the application store's todos property is changed.

@State()

The @State() decorator is used to identify a state property in the application store. Identifying state properties allow the property to be automatically updated when the application store's property changes.

@Store()
class TodoListComponent {
   @State() todos:Todo[] = [];
   ...
}

In the above example we are declaring that the todos property of the TodoListComponent should be automatically updated whenever the application store's todos property is changed. Please also refer to the @Store() equivalent.

@InitialState(state: any)

The @InitialState decorator is used for setting the initial state of the application store.

This decorator accepts a single object state that describes the initial state of the application.

@InitialState({
    count: 0
})

License

MIT