ngrx-immer

Immer wrappers around NgRx methods to mutate state easily

Installation

npm install ngrx-immer

Do not forget to install immer

Resources

• Immer docs
• NgRx docs

createImmerReducer

Creates an NgRx reducer, but allows you to mutate state without having to use to spread operator.

• Use it when you want to go Immer all the way
• Caveat, you have to return the state with each on method

import { createImmerReducer } from 'ngrx-immer/store';

const todoReducer = createImmerReducer(
	{ todos: [] },
	on(newTodo, (state, action) => {
		state.todos.push({ text: action.todo, completed: false });
		return state;
	}),
	on(completeTodo, (state, action) => {
		state.todos[action.index].completed = true;
		return state;
	}),
);

immerOn

Creates an NgRx reducer, but allows you to mutate state without having to use to spread operator.

• Use it when you want to go sprinkle a little bit of Immer for more complex cases

import { immerOn } from 'ngrx-immer/store';

const todoReducer = createReducer(
	{ todos: [] },
	on(newTodo, (state, action) => {
		return {
			...state,
			todos: [...state.todos, action.todo],
		};
	}),
	immerOn(completeTodo, (state, action) => {
		state.todos[action.index].completed = true;
	}),
);

ImmerComponentStore

Wraps Immer around the Component Store updater and setState methods.

import { ImmerComponentStore } from 'ngrx-immer/component-store';

@Injectable()
export class MoviesStore extends ImmerComponentStore<MoviesState> {
	constructor() {
		super({ movies: [] });
	}

	readonly addMovie = this.updater((state, movie: Movie) => {
		state.movies.push(movie);
	});
}

immerPatchState

Provides an Immer-version of the patchState function from the @ngrx/signals package. In addition to partial state objects and updaters that update the state immutably, it accepts updater functions that update the state in a mutable manner. Similar to patchState, the immerPatchState function can be used to update the state of both SignalStore and SignalState.

const UserStore = signalStore(
	withState({
		user: { firstName: 'Konrad', lastName: 'Schultz' },
		address: { city: 'Vienna', zip: '1010' },
	}),
	withMethods((store) => ({
		setLastName(lastName: string): void {
			immerPatchState(store, (state) => {
				state.user.lastName = lastName;
			});
		},
		setCity(city: string): void {
			immerPatchState(store, (state) => {
				state.address.city = city;
			});
		},
	}))
);

Please note, that the updater function can only mutate a change without returning it or return an immutable state without mutable change.

This one is going to throw a runtime error:

// will throw because of both returning and mutable change
immerPatchState(userStore, (state) => {
	state.name.lastname = 'Sanders'; // mutable change
	return state; // returning state
});

immerReducer

Inspired by Alex Okrushko, immerReducer is a reducer method that uses the Immer produce method. This method is used by all the methods in ngrx-immer provides.

FAQ

• See the Immer docs, Update patterns, on how to mutate state