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@ngxp/store-service

Adds an abstraction layer between Angular components and the @ngrx store and effects. This decouples the components from the store, selectors, actions and effects and makes it easier to test components.

Table of contents

• Installation
• Comparison
  • Before
  • After
• Documentation
  • StoreService
  • Selectors
  • Actions
  • Observers
    • Observe multiple types
    • Use objects with type property
    • String action types
    • Custom mapper
  • Deprecated Annotations
• Testing
  • Testing Components
    • Testing Selectors
    • Testing Actions
    • Testing Observers
  • Testing StoreService
    • Testing StoreService Selectors
    • Testing StoreService Actions
    • Testing StoreService Observers
• Examples
  • Example Store Service
  • Example Tests

Installation

Get the latest version from NPM

npm install @ngxp/store-service

Comparison

Before

Component

import { Component } from '@angular/core';
import { Observable } from 'rxjs';
import { Book } from 'src/app/shared/books/book.model';
// Tight coupling to ngrx, state model, selectors and actions
import { Store } from '@ngrx/store'; 
import { Actions, ofType } from '@ngrx/effects'; 
import { AppState } from 'src/app/store/appstate.model';
import { getAllBooks, getBook } from 'src/app/store/books/books.selectors'; 
import { addBookAction, booksLoadedAction } from 'src/app/store/books/books.actions'; 
 
@Component({
    selector: 'nss-book-list',
    templateUrl: './book-list.component.html',
    styleUrls: ['./book-list.component.scss']
})
export class BookListComponent {

    books$: Observable<Book[]>;
    book$: Observable<Book>;
    booksLoaded: boolean = false;

    constructor(
        private store: Store<AppState>
        private actions: Actions
    ) {
        this.books$ = this.store.select(getAllBooks);
        this.book$ = this.store.select(getBook, { id: 0 });
        this.actions
            .pipe(
                ofType(booksLoadedAction),
                map(() => this.loaded = true)
            )
            .suscribe();
    }

    addBook(book: Book) {
        this.store.dispatch(addBookAction({ book }));
    }
}

After

Component

import { Component } from '@angular/core';
import { Observable } from 'rxjs';
import { Book } from 'src/app/shared/books/book.model';
import { BookStoreService } from 'src/app/shared/books/book-store.service'; 
// Reduced to just one dependency. Loose coupling

@Component({
    selector: 'nss-book-list',
    templateUrl: './book-list.component.html',
    styleUrls: ['./book-list.component.scss']
})
export class BookListComponent {

    books$: Observable<Book[]>;
    book$: Observable<Book>;
    booksLoaded: boolean = false;

    constructor(
        private bookStore: BookStoreService // <- StoreService
    ) {
        this.books$ = this.bookStore.getAllBooks(); // <- Selector
        this.book$ = this.bookStore.getBook({ id: 0 }); // <- Selector
        this.bookStore.booksLoaded$ // <-- Observer / Action stream of type
            .pipe(
                map(() => this.loaded = true)
            )
            .subscribe();
    }

    addBook(book: Book) {
        this.bookStore.addBook({ book }); // <- Action
    }
}

BookStoreService

import { Injectable } from '@angular/core';
import { select, StoreService, dispatch, observe } from '@ngxp/store-service';
import { Book } from 'src/app/shared/books/book.model';
import { getBooks } from 'src/app/store/books/books.selectors';
import { State } from 'src/app/store/store.model';
import { addBookAction, booksLoadedAction } from 'src/app/store/books/books.actions';

@Injectable()
export class BookStoreService extends StoreService<State> {

    getAllBooks = select(getBooks); // <- Selector

    getBook = select(getBook); // <- Selector

    addBook = dispatch(addBookAction); // <- Action

    booksLoaded$ = observe([booksLoadedAction]); // <- Observer / Action stream
}

Documentation

StoreService

The BookStoreService Injectable class has to extend the StoreService<State> class where State is your ngrx state model.

import { StoreService } from '@ngxp/store-service';
import { AppState } from 'app/store/state.model';

@Injectable()
export class BookStoreService extends StoreService<AppState> {
    ...
}

Selectors

To use selectors you wrap the ngrx selector inside the select(...) function:

// Define the selector function
export const selectAllBooks = createSelector(
    (state: State) => state.books;
};

//Or with props
export const selectBook = createSelector(
    (state: State, props: { id: number }) => state.books[id];
};
...

// Use the selector function inside the select(...) function
allBooks = select(selectAllBooks); // () => Observable<Book[]>

book = select(selectBook); // (props: { id: number }) => Observable<Book>

The select(...) function automatically infers the correct typing according to the props and return type of the selector.

Actions

To dispatch actions add a property with the dispatch(...) function.

// Defined the Action as a class
export const loadBooksAction = createAction('[Books] Load books');

export const addBookAction = createAction('[Books] Add book' props<{ book: Book}>())

...
loadBooks = dispatch(loadBooksAction); // () => void

addBook = dispatch(addBookAction); // (props: { book: Book }) => void

The dispatch(...) function automatically infers the parameters according to the props of the action.

Observers

Observers are a way to listen for specific action types on the Actions stream from @ngrx/effects.

booksLoaded$ = observe([booksLoadedAction]);

Multiple types

You can provide multiple types, just like in the ofType(...) pipe.

booksLoaded$ = observe([booksLoadedAction, booksLoadFailedAction]);

Custom mapper

The observe(...) function has an additional parameter to provide a custom customMapper mapping function. Initially this will be:

action => action

To use a custom mapper, provide it as second argument in the observe(...) function.

export const toData = action => action.data;

...
dataLoaded$ = observe([dataLoadedAction], toData);

Deprecated Annotations

Before Version 12 the Store Service used annotations instead of functions. This old way still works but is deprecated and will be removed in the future.

import { Select, StoreService, Dispatch, Selector, Dispatcher, Observe } from '@ngxp/store-service';

@Select(getBooks)
getAllBooks: Selector<typeof getBooks>;

@Dispatch(addBookAction)
addBook: Dispatcher<typeof addBookAction>;

@Observe([dataLoadedAction], toData)
dataLoaded$: Observable<Book[]>;

Testing

Testing your components and the StoreService is easy. The @ngxp/store-service/testing package provides useful test-helpers to reduce testing friction.

Testing Components

Testing Selectors

To test selectors you provide the StoreService using the provideStoreServiceMock method in the testing module of your component. Then get the StoreServiceMock<T> instance using the getStoreServiceMock helper function.

import { provideStoreServiceMock, StoreServiceMock, getStoreServiceMock } from '@ngxp/store-service/testing';
...
let bookStoreService: StoreServiceMock<BookStoreService>;
...
TestBed.configureTestingModule({
    declarations: [
        BookListComponent
    ],
    providers: [
        provideStoreServiceMock(BookStoreService)
    ]
})
...
bookStoreService = getStoreServiceMock(BookStoreService);

The StoreServiceMock class replaces all selector functions on the store service class with a BehaviorSubject. So now you can do the following to emit new values to the observables:

bookStoreService.getAllBooks().next(newBooks);

The BehaviorSubject is initialized with the value being undefined. If you want a custom initial value, the provideStoreServiceMock method offers an optional parameter. This is an object of key value pairs where the key is the name of the selector function, e.g. getAllBooks.

import { provideStoreServiceMock, StoreServiceMock, getStoreServiceMock } from '@ngxp/store-service/testing';
...
let bookStoreService: StoreServiceMock<BookStoreService>;
...
TestBed.configureTestingModule({
    declarations: [
        BookListComponent
    ],
    providers: [
        provideStoreServiceMock(BookStoreService, {
            getAllBooks: []
        })
    ]
})
...
bookStoreService = getStoreServiceMock(BookStoreService);

The BehaviorSubject for getAllBooks is now initialized with an empty array instead of undefined.

Testing Actions

To test if a component calls the dispatch methods you provide the StoreService using the provideStoreServiceMock method in the testing module of your component. Then get the StoreServiceMock<T> instance using the getStoreServiceMock helper function.

You can then spy on the method as usual.

import { provideStoreServiceMock, StoreServiceMock } from '@ngxp/store-service/testing';
...
let bookStoreService: StoreServiceMock<BookStoreService>;
...
TestBed.configureTestingModule({
    declarations: [
        NewBookComponent
    ]
    imports: [
        provideStoreServiceMock(BookStoreService)
    ]
})
...
it('adds a new book', () => {
    const book: Book = getBook();
    const addBookSpy = jest.spyOn(bookStoreService, 'addBook');

    component.book = book;
    component.addBook();

    expect(addBookSpy).toHaveBeenCalledWith({ book });
});

Testing Observers

To test observers inside components you provide the StoreService using the provideStoreServiceMock method in the testing module of your component. Then get the StoreServiceMock<T> instance using the getStoreServiceMock helper function.

import { provideStoreServiceMock, StoreServiceMock, getStoreServiceMock } from '@ngxp/store-service/testing';
...
let bookStoreService: StoreServiceMock<BookStoreService>;
...
TestBed.configureTestingModule({
    declarations: [
        BookListComponent
    ],
    providers: [
        provideStoreServiceMock(BookStoreService)
    ]
})
...
bookStoreService = getStoreServiceMock(BookStoreService);

The StoreServiceMock class replaces all observer properties on the store service class with a BehaviorSubject. So now you can do the following to emit new values to the subscribers:

bookStoreService.booksLoaded$().next(true);

The BehaviorSubject is initialized with the value being undefined. If you want a custom initial value, the provideStoreServiceMock method offers an optional parameter. This is an object of key value pairs where the key is the name of the observer property, e.g. booksLoaded$.

import { provideStoreServiceMock, StoreServiceMock, getStoreServiceMock } from '@ngxp/store-service/testing';
...
let bookStoreService: StoreServiceMock<BookStoreService>;
...
TestBed.configureTestingModule({
    declarations: [
        BookListComponent
    ],
    providers: [
        provideStoreServiceMock(BookStoreService, {
            booksLoaded$: false
        })
    ]
})
...
bookStoreService = getStoreServiceMock(BookStoreService);

The BehaviorSubject for booksLoaded$ is now initialized with false instead of undefined.

Testing StoreService

To test the StoreService itself you use the provided test helpers from @ngrx/store/testing and @ngrx/effects/testing.

Testing StoreService Selectors

You can provide mocks for selectors with the provideMockStore from @ngrx/store/testing a. See (@ngrx/store Testing)[https://ngrx.io/guide/store/testing] for their documentation.

Mock the selectors using the provideMockStore function and check if the StoreService returns an Observable with the mocked value.

import { MockStore, provideMockStore, getStoreServiceMock } from '@ngrx/store/testing';
import { BookStoreService } from 'src/app/shared/books/book-store.service';
import { selectBook, selectBooks } from '../../store/books/books.selectors';

describe('BookStoreService', () => {
    let bookStoreService: BookStoreService;
    let mockStore: MockStore<{ books: BookState }>;

    const books: Book[] = [
        {
            author: 'Joost',
            title: 'Testing the StoreService',
            year: 2019
        }
    ];

    beforeEach(waitForAsync(() => {
        TestBed.configureTestingModule({
            providers: [
                BookStoreService,
                provideMockStore({
                    selectors: [
                        {
                            selector: selectBooks,
                            value: books
                        },
                        {
                            selector: selectBook,
                            value: books[0]
                        }
                    ]
                })
            ]
        });
    }));

    beforeEach(() => {
        bookStoreService = getStoreServiceMock(BookStoreService);
        mockStore = TestBed.inject(Mockstore);
    });

    it('executes the getBooks Selector', () => {
        const expected = cold('a', { a: books });

        expect(bookStoreService.getAllBooks()).toBeObservable(expected);
    });
    it('executes the getBook Selector', () => {
        const expected = cold('a', { a: books[0] });

        expect(bookStoreService.getBook({ id: 0 })).toBeObservable(expected);
    });
});

Testing StoreService Actions

You can provide mocks for selectors with the provideMockStore from @ngrx/store/testing a. See (@ngrx/store Testing)[https://ngrx.io/guide/store/testing] for their documentation.

Mock the selectors using the provideMockStore function and check if the StoreService returns an Observable with the mocked value.

To test if the StoreService dispatches the correct actions the MockStore from @ngrx has a property called scannedActions$. This is an Observable of all dispatched actions to check if an action was dispatched correctly.

import { MockStore, provideMockStore, getStoreServiceMock } from '@ngrx/store/testing';
import { cold } from 'jest-marbles';
import { BookStoreService } from 'src/app/shared/books/book-store.service';
import { addBookAction, loadBooksAction } from '../../store/books/books.actions';

describe('BookStoreService', () => {
    let bookStoreService: BookStoreService;
    let mockStore: MockStore<{ books: BookState }>;

    beforeEach(waitForAsync(() => {
        TestBed.configureTestingModule({
            providers: [
                BookStoreService,
                provideMockStore()
            ]
        });
    }));

    beforeEach(() => {
        bookStoreService = getStoreServiceMock(BookStoreService);
        mockStore = TestBed.inject(MockStore);
    });

    it('dispatches a new addBookAction', () => {
        const book: Book = getBook();
        bookStoreService.addBook({ book });

        const expected = cold('a', { a: addBookAction({ book }) });
        expect(mockStore.scannedActions$).toBeObservable(expected);
    });
    it('dispatches a new loadBooksAction', () => {
        bookStoreService.loadBooks();

        const expected = cold('a', { a: loadBooksAction() });
        expect(mockStore.scannedActions$).toBeObservable(expected);
    });
});

Testing StoreService Observers

To test the observers / actions stream, you import the provideMockActions from @ngrx/effects/testing inside the testing module. Then check if the Observer filters the correct actions.

import { getStoreServiceMock } from '@ngxp/store-service/testing';
import { provideMockActions } from '@ngrx/effects/testing';
import { BehaviorSubject } from 'rxjs';
import { BookStoreService } from 'src/app/shared/books/book-store.service';
import { booksLoadedAction } from '../../store/books/books.actions';

describe('BookStoreService', () => {
    let bookStoreService: BookStoreService;
    const mockActions = new BehaviorSubject(undefined);

    beforeEach(waitForAsync(() => {
        TestBed.configureTestingModule({
            providers: [
                BookStoreService,
                provideMockActions(mockActions)
            ]
        });
    }));

    beforeEach(() => {
        bookStoreService = getStoreServiceMock(BookStoreService);
    });

    it('filters the BooksLoadedActions in booksLoaded$', () => {
        const expectedValue: Book[] = [{
            author: 'Author',
            title: 'Title',
            year: 2018
        }];

        const action = booksLoadedAction({ books: expectedValue });
        mockActions.next(action);

        const expected = cold('a', { a: action });
        
        expect(bookStoreService.booksLoaded$()).toBeObservable(expected);
    });
});

Examples

For detailed examples of all this have a look at the Angular Project in the apps/store-service-sample folder.

Example Store Service

Have a look at the BookStoreService

Example Tests

For examples on Component Tests please have look at the test for the BookListComponent and the NewBookComponent

Testing the StoreService is also very easy. For an example have a look at the BookStoreService