@ngxs-labs/emitter

---

ER is a new pattern that provides the opportunity to feel free from actions

🚀 See it in action on Stackblitz

This package allows you to get rid of actions. You can use decorators to register actions directly in your state, you don't have to create any actions in your project (until you really need them), as they don't give any profit, only bring extra boilerplate files.

Concepts

We've simplified this flow and threw out unnecessary mediators:

:package: Install

To install @ngxs-labs/emitter run the following command:

npm install @ngxs-labs/emitter
# or if you use yarn
yarn add @ngxs-labs/emitter

:hammer: Usage

Import the module into your root application module:

import { NgModule } from '@angular/core';
import { NgxsEmitPluginModule } from '@ngxs-labs/emitter';

@NgModule({
    imports: [
        ...,
        NgxsEmitPluginModule.forRoot()
    ]
})
export class AppModule {}

Receiver

Receiver is a basic building block. @Receiver() is a function that allows you to decorate static methods in your states for further passing this method to the emitter:

import { State, StateContext } from '@ngxs/store';
import { Receiver, EmitterAction } from '@ngxs-labs/emitter';

export interface CounterStateModel {
    value: number;
}

@State<CounterStateModel>({
    name: 'counter',
    defaults: {
        value: 0
    }
})
export class CounterState {
    @Receiver()
    public static setValue({ setState }: StateContext<CounterStateModel>, { payload }: EmitterAction<number>) {
        setState({
            value: payload
        });
    }
}

Emitter

Emitter is basically a bridge between your component and receivers. @Emitter() is a function that decorates properties defining new getter and gives you an access to the emittable interface:

import { Select } from '@ngxs/store';
import { Emitter, Emittable } from '@ngxs-labs/emitter';

import { CounterStateModel, CounterState } from './counter.state';

@Component({
    selector: 'app-counter',
    template: `
        <ng-container *ngIf="count$ | async as count">
            <h3>Count is {{ count.value }}</h3>
            <div>
                <button (click)="counterValue.emit(count.value + 1)">Increment (+1)</button>
                <button (click)="counterValue.emit(count.value - 1)">Decrement (-1)</button>
            </div>
        </ng-container>  
    `
})
export class CounterComponent {
    @Select(CounterState)
    public count$: Observable<CounterStateModel>;

    // Use in components to emit asynchronously payload
    @Emitter(CounterState.setValue)
    public counterValue: Emittable<number>;
}

Custom types

You can define custom types for debbuing purposes (works with @ngxs/logger-plugin):

import { State, StateContext } from '@ngxs/store';
import { Receiver } from '@ngxs-labs/emitter';

@State<number>({
    name: 'counter',
    defaults: 0
})
export class CounterState {
    @Receiver({
        type: '[Counter] Increment value'
    })
    public static increment({ setState, getState }: StateContext<number>) {
        setState(getState() + 1);
    }

    @Receiver({
        type: '[Counter] Decrement value'
    })
    public static decrement({ setState, getState }: StateContext<number>) {
        setState(getState() - 1);
    }
}

Actions

If you still need actions - it is possible to pass an action as an argument into @Receiver() decorator:

import { State, StateContext } from '@ngxs/store';
import { Receiver } from '@ngxs-labs/emitter';

export class Increment {
    public static type = '[Counter] Increment value';
}

export class Decrement {
    public static type = '[Counter] Decrement value';
}

@State<number>({
    name: 'counter',
    defaults: 0
})
export class CounterState {
    @Receiver({
        action: Increment
    })
    public static increment({ setState, getState }: StateContext<number>) {
        setState(getState() + 1);
    }

    @Receiver({
        action: Decrement
    })
    public static decrement({ setState, getState }: StateContext<number>) {
        setState(getState() - 1);
    }
}

Dependency injection

Assume you have to make some API request and load some data from your server, it is very easy to use services with static methods, Angular provides an Injector class for getting instances by reference:

import { Injector } from '@angular/core';

import { State, StateContext } from '@ngxs/store';
import { Receiver } from '@ngxs-labs/emitter';

import { tap } from 'rxjs/operators/tap';

interface Todo {
    userId: number;
    id: number;
    title: string;
    completed: boolean;
}

@State<Todo[]>({
    name: 'counter',
    defaults: []
})
export class TodosState {
    // ApiService is a class that is defined somewhere...
    public static api: ApiService;

    constructor(injector: Injector) {
        TodosState.api = injector.get<ApiService>(ApiService);
    }

    @Receiver()
    public static getTodos({ setState }: StateContext<Todo[]>) {
        // If `ApiService.prototype.getTodos` returns an Observable - just use `tap` operator
        return this.api.getTodos().pipe(
            tap((todos) => setState(todos))
        );

        // If `ApiService.prototype.getTodos` returns a Promise - just use `then`
        return this.api.getTodos().then((todos) => setState(todos));
    }
}

If you work with promises - we advice you to use async/await approach, because method marked with async keyword will automatically return a Promise, you will not get confused if you missed return keyword somewhere:

import { Injector } from '@angular/core';

import { State, StateContext } from '@ngxs/store';
import { Receiver } from '@ngxs-labs/emitter';

export interface AppInformationStateModel {
    version: string;
    shouldUseGraphql: boolean;
}

@State<AppInformationStateModel>({
    name: 'information',
    defaults: null
})
export class AppInformationState {
    public static appService: AppService;

    constructor(injector: Injector) {
        AppInformationState.appService = injector.get<AppService>(AppService);
    }

    @Receiver({
        type: '[App information] Get app information'
    })
    public static async getAppInformation({ setState }: StateContext<AppInformationStateModel>) {
        setState(
            await this.appService.getAppInformation()
        );
    }
}

Lifecycle

As you may know - actions in NGXS have own lifecycle. We also provide RxJS operators that give you the ability to react to actions at different points in their existence:

• ofEmittableDispatched: triggers when an emittable target has been dispatched
• ofEmittableSuccessful: triggers when an emittable target has been completed successfully
• ofEmittableCanceled: triggers when an emittable target has been canceled
• ofEmittableErrored: triggers when an emittable target has caused an error to be thrown

Below is just a simple example that uses those operators:

import { State } from '@ngxs/store';
import { Receiver } from '@ngxs-labs/emitter';

@State<number>({
    name: 'counter',
    defaults: 0
})
class CounterState {
    @Receiver()
    public static increment({ setState, getState }: StateContext<number>) {
        setState(getState() + 1);
    }

    @Receiver()
    public static decrement({ setState, getState }: StateContext<number>) {
        setState(getState() - 1);
    }

    @Receiver()
    public static multiplyBy2({ setState, getState }: StateContext<number>) {
        setState(getState() * 2);
    }

    @Receiver()
    public static throwError() {
        return throwError(new Error('Whoops!'));
    }
}

Import operators in component and pipe Actions service:

import { Actions } from '@ngxs/store';
import {
    Emitter,
    Emittable,
    ofEmittableDispatched,
    OfEmittableActionContext
} from '@ngxs-labs/emitter';

import { CounterState } from './counter.state';

@Component({
    selector: 'app-root',
    template: ''
})
export class AppComponent {
    @Emitter(CounterState.increment)
    private increment: Emittable<void>;

    @Emitter(CounterState.decrement)
    private decrement: Emittable<void>;

    constructor(private actions$: Actions) {
        this.actions$.pipe(
            ofEmittableDispatched(CounterState.increment)
        ).subscribe(({ type }: OfEmittableActionContext<void>) => {
            console.log(type === 'CounterState.increment'); // true
        });

        setInterval(() => {
            this.increment.emit();
            this.decrement.emit();
        }, 1000);
    }
}