A framework-agnostic RxJS effects implementation

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Effects

First, we need to initialize the the library by calling the initEffects() function:

import { initEffects } from '@ngneat/effects';

initEffects();

Actions are created by using the createAction or actionsFactory functions:

import { actionsFactory, createAction, props } from '@ngneat/effects';

// todos.actions.ts
export interface Todo {
  id: string;
  name: string;
}

export const addTodo = createAction('[Todos] Add Todo', props<{ title: string }>());

// We recommend using the actions factory to prefix each action 
// for better readability and debug purposes when using redux dev tools
export const todoActions = actionsFactory('todo');

// We can declare an action by passing it a type and an optional payload. 
export const loadTodos = todoActions.create('Load Todos')
export const addTodo   = todoActions.create('Add Todo', props<Todo>())

Next, we need to define the effects, and register them:

import { createEffect, registerEffects, ofType } from '@ngneat/effects';

export const addTodo$ = createEffect((actions) =>
  actions.pipe(
    ofType(addTodo),
    tap(console.log)
  )
);

registerEffects([addTodo$])

Finally, we can dispatch actions using the dispatch function:

import { dispatch } from '@ngneat/effects';

dispatch(addTodo({ title: 'effects' }));

Use with React

First, install the package: npm i @ngneat/effects-hook.

Now, we can use the useEffects hook and pass our effects:

import { useEffects } from '@ngneat/effects-hook';
import { dispatch }   from '@ngneat/effects';
import { useEffect }  from 'react';

export function TodosPage() {
  useEffects([loadTodos$, addTodo$]);

  useEffect(() => dispatch(loadTodos()), []);

  return (
    <button onClick = {() => dispatch(addTodo({ title: 'foo' }))}>
      Add
    </button>
  )
}

The effects we pass are tied to the component life cycle hook and will be destroyed with the component.

Use with Angular

First, install the package: npm i @ngneat/effects-ng.

Next, create the effect provider:

import { createEffect } from '@ngneat/effects';

@Injectable({ providedIn: 'root' })
export class TodosEffects {

  constructor(private todosApi: TodosApi) {}

  loadTodos$ = createEffect(actions => actions.pipe(
    ofType(loadTodos),
    switchMap((todo) => this.todosApi.loadTodos())
  ));
}

By default, the return value of an effect doesn't dispatch an action. You can get this behavior by passing the { dispatch: false } option as a second parameter.

Then we need to register our the effects in our app module:

import { EffectsNgModule } from '@ngneat/effects-ng';
import { TodosEffects }    from 'todos/todos.effect.ts';

@NgModule({
  imports: [
    EffectsNgModule.forRoot([TodosEffects], { dispatchByDefault: false }),
  ]
})
export class AppModule {
}

The forRoot method can take as its second parameter the global configuration. We can set the dispatchByDefault property to true for each effect to dispatch the resulting action. The default is set to false.

As stated above, this behavior can be overwritten on each effect.

In order to register lazily loaded effects use the forFeature method:

import { EffectsNgModule } from '@ngneat/effects-ng';
import { PostsEffects }    from "posts/posts.effect.ts"

@NgModule({
  imports: [
    EffectsNgModule.forFeature([PostsEffects])
  ]
})
export class LazyModule {
}

The actions can be dispatched by injecting the Actions provider:

import { Actions } from '@ngneat/effects-ng';

@Component(...)
export class AppComponent {
  constructor(private actions: Actions) {}

  ngOnInit() {
    this.actions.dispatch(loadTodos());
  }
}

Testing

In order to test effect classes and using the actions stream from parameter you can substitute the action stream by a custom created action stream. It's recommended to only use this feature for testing purposes.

describe("Effect test", () => {
  // use a custom action stream to replace the stream before each test
  let customActionsStream: Actions;

  beforeEach(() => {
    customActionsStream = new Actions();

    TestBed.configureTestingModule({
      imports: [
        EffectsNgModule.forRoot(
          [EffectsOne],
          { customActionsStream }
        )
      ]
    });
  })
})

Effect Functions

To use an effect function we first need to create it by using the createEffectFn function:

import { createEffectFn } from '@ngneat/effects';

export const searchTodoEffect = createEffectFn((searchTerm$: Observable<string>) => {
  return searchTerm$.pipe(
    debounceTime(300),
    switchMap((searchTerm) => fetchTodos({ searchTerm })),
  );
});

The createEffectFn function takes a callback function which is passed an Observable parameter and returns an Observable.

Use with React

First, install the package: npm i @ngneat/effects-hook.

We can register the effect in our component, and call it when we need:

import { useEffectFn } from '@ngneat/effects-hooks';

function SearchComponent() {
  const searchTodo = useEffectFn(searchTodoEffect);

  return <input onChange = {({ target: { value } }) => searchTodo(value) }/>
}

Every time the effect is called, its value is pushed into that Observable.

We can also register multiple effects:

function FooComponent() {
  const [addTodo, updateTodo, deleteTodo] = useEffectFn([
    addTodoEffect, updateTodoEffect, deleteTodoEffect
  ]);

  return ...
}

First, install the package: npm i @ngneat/effects-ng.

Create an effect class, extends the EffectFn class and use the createEffectFn method to create your effects:

import { EffectFn } from '@ngneat/effects-ng';

export class TodosEffects extends EffectFn {

  searchTodo = this.createEffectFn((searchTerm$: Observable<string>) => 
    searchTerm$.pipe(
      debounceTime(300),
      switchMap((searchTerm) => fetchTodos({ searchTerm })),
    );
  );
}

Inject the effects provider in your component, and call it when you need:

@Component({
  providers: [TodosEffects],
})
export class TodosComponent {
  constructor(private todosEffects: TodosEffects) {
  }

  ngOnInit() {
    this.control.valueChanges.subscribe(searchTerm => {
      this.todosEffects.searchTodo(searchTerm);
    });
  }
}