ngrx-immer

Immer wrappers around NgRx methods to simplify mutating state

• ngrx-immer
  • Installation
  • Functions
  • createImmerReducer (@ngrx/store)
  • immerOn (@ngrx/store)
  • ImmerComponentStore (@ngrx/component-store)
  • immerPatchState (@ngrx/signals)
  • immerReducer
  • FAQ
  • Resources

Installation

npm install ngrx-immer

Do not forget to install immer

Functions

createImmerReducer (@ngrx/store)

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 (@ngrx/store)

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 (@ngrx/component-store)

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 (@ngrx/signals)

[!IMPORTANT]
Because @ngrx/signals is in developer preview, the immerPatchState function is also in developer preview. It is ready to try, but may change before becoming stable.

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

Resources

• Immer docs
• NgRx docs