NgSimpleState. Simple state management in Angular with only Services and RxJS or Signal.

#angular #javascript #typescript

One of the most challenging things in software development is state management. Currently there are several state management libraries for Angular apps: NGRX, NGXS, Akita...

But what if you don't want to learn, setup, and deal with all the boilerplate for a simple project, what if you want to manage state by only using tools you already know well as an Angular developer.

In this write up, I'll show you a simple way of managing state by only using RxJS and Dependency Injection with NgSimpleState.

Step 1: install `ng-simple-state`

npm i ng-simple-state

Step 2: Import provideNgSimpleState into your providers

import { isDevMode } from '@angular/core';
import { bootstrapApplication } from '@angular/platform-browser';

import { AppComponent } from './app.component';
import { provideNgSimpleState } from 'ng-simple-state';

bootstrapApplication(AppComponent, {
  providers: [
    provideNgSimpleState({
      enableDevTool: isDevMode(),
      persistentStorage: 'local'
    })
  ]
});

Step 3: Create your store

This is an example for a counter store in a src/app/counter-store.ts file.
Obviously, you can create every store you want with every complexity you need.

1) Define yuor state interface, eg.:

export interface CounterState {
    count: number;
}

2) Define your store service by extending NgSimpleStateBaseRxjsStore or NgSimpleStateBaseSignalStore, eg.:

import { Injectable } from '@angular/core';
import { NgSimpleStateBaseRxjsStore } from 'ng-simple-state';

export interface CounterState {
    count: number;
}

@Injectable()
export class CounterStore extends NgSimpleStateBaseRxjsStore<CounterState> {

}

3) Implement initialState() method and provide the initial state of the store, eg.:

import { Injectable } from '@angular/core';
import { NgSimpleStateBaseRxjsStore } from 'ng-simple-state';

export interface CounterState {
    count: number;
}

@Injectable()
export class CounterStore extends NgSimpleStateBaseRxjsStore<CounterState> {

  initialState(): CounterState {
    return {
      count: 0
    };
  }

}

4) Implement one or more selectors of the partial state you want, in this example selectCount() eg.:

import { Injectable } from '@angular/core';
import { NgSimpleStateBaseRxjsStore } from 'ng-simple-state';
import { Observable } from 'rxjs';

export interface CounterState {
    count: number;
}

@Injectable()
export class CounterStore extends NgSimpleStateBaseRxjsStore<CounterState> {

  initialState(): CounterState {
    return {
      count: 0
    };
  }

  selectCount(): Observable<number> {
    return this.selectState(state => state.count);
  }
}

5) Implement one or more actions for change the store state, in this example increment() and decrement() eg.:

import { Injectable } from '@angular/core';
import { NgSimpleStateBaseRxjsStore } from 'ng-simple-state';
import { Observable } from 'rxjs';

export interface CounterState {
  count: number;
}

@Injectable()
export class CounterStore extends NgSimpleStateBaseRxjsStore<CounterState> {

  initialState(): CounterState {
    return {
      count: 0
    };
  }

  selectCount(): Observable<number> {
    return this.selectState(state => state.count);
  }

  increment(increment: number = 1): void {
    this.setState(state => ({ count: state.count + increment }));
  }

  decrement(decrement: number = 1): void {
    this.setState(state => ({ count: state.count - decrement }));
  }
}

Step 3: Use your store into the components, eg.:

import { Component, inject } from '@angular/core';
import { Observable } from 'rxjs';
import { CounterStore } from './counter-store';

@Component({
  selector: 'app-root',
  imports: [CounterStore],
  template: `
  <h1>Counter: {{ counter$ | async }}</h1>
  <button (click)="counterStore.decrement()">Decrement</button>
  <button (click)="counterStore.increment()">Increment</button>
  `,
})
export class AppComponent {
  public counterStore = inject(CounterStore);
  public counter$: Observable<number>;
}