Entity

Entity provides an API to manipulate and query entity collections.

• Provides performant CRUD operations for managing entity collections.
• Extensible type-safe adapters for selecting entity information. Example:

/**
 * @ngrx/entity provides a predefined interface for handling
 * a structured dictionary of records. This interface
 * includes an array of ids, and a dictionary of the provided
 * model type by id. This interface is extended to include
 * any additional interface properties.
 */
export interface State extends EntityState<Book> {
  selectedBookId: string | null;
}

/**
 * createEntityAdapter creates an object of many helper
 * functions for single or multiple operations
 * against the dictionary of records. The configuration
 * object takes a record id selector function and
 * a sortComparer option which is set to a compare
 * function if the records are to be sorted.
 */
export const adapter: EntityAdapter<Book> = createEntityAdapter<Book>({
  selectId: (book: Book) => book.id,
  sortComparer: false,
});

/**
 * getInitialState returns the default initial state
 * for the generated entity state. Initial state
 * additional properties can also be defined.
 */
export const initialState: State = adapter.getInitialState({
  selectedBookId: null,
});

export const reducer = createReducer(
  initialState,
  /**
   * The addMany function provided by the created adapter
   * adds many records to the entity dictionary
   * and returns a new state including those records. If
   * the collection is to be sorted, the adapter will
   * sort each record upon entry into the sorted array.
   */
  on(
    BooksApiActions.searchSuccess,
    CollectionApiActions.loadBooksSuccess,
    (state, { books }) => adapter.addMany(books, state)
  ),
  /**
   * The addOne function provided by the created adapter
   * adds one record to the entity dictionary
   * and returns a new state including that records if it doesn't
   * exist already. If the collection is to be sorted, the adapter will
   * insert the new record into the sorted array.
   */
  on(BookActions.loadBook, (state, { book }) => adapter.addOne(book, state)),
  on(ViewBookPageActions.selectBook, (state, { id }) => ({
    ...state,
    selectedBookId: id,
  }))
);