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Update State

Use setState to update the state of a Feature Store right away. setState accepts a Partial Type. This allows us to pass only some properties of a bigger state interface.

selectTodo(id: number) {
this.setState({selectedTodoId: id});

Do you need to update the state based on the current state? setState accepts a callback function which gives you access to the current state.

// Update state based on current state
addTodo(todo: Todo) {
this.setState(state => ({
todos: [...state.todos, todo]

For better logging in the JS Console / Redux DevTools you can provide an optional name to the setState function:

this.setState({selectedTodoId: id}, 'selectTodo');

Use an Observable to update state

setState also accepts an Observable. This can be useful if your feature state depends on the values of an Observable. You just have to make sure that the Observable, which is passed to setState, emits values with the (partial) type of your state interface.

Example code from the MiniRx Demo:

import { FeatureStore } from "mini-rx-store";
import { map, Observable, timer } from "rxjs";

interface ArtState {
opacity: number;

const initialState: ArtState = {
opacity: 1,

export class ArtStoreService extends FeatureStore<ArtState> {
opacity$: Observable<number> = => state.opacity);

constructor() {
super('art', initialState);

const delayedOpacity$: Observable<ArtState> = timer(Math.random() * 5000).pipe(
map(() => ({ opacity: Math.random() })) // map data to ArtState

this.setState(delayedOpacity$); // setState will be triggerd by the Observable

In this example, you can see that there is no further subscription code needed on delayedOpacity$. The subscription (and the cleanup of the subscription) happens internally.

Undo setState Actions with undo

We can easily undo setState actions with the Undo Extension installed.

Calling setState returns an action which can be used to perform an Undo.

import { Action } from 'mini-rx-store';

removeTodo(id: number): Action {
return this.setState(state => ({
todos: state.todos.filter(item => !== id)

removeAndUndo() {
const todoRemoveAction: Action = this.removeTodo(2);