@angular/cdk/collections#DataSource TypeScript Examples

class FakeDataSource extends DataSource<any> {
  connect(collectionViewer: CollectionViewer): Observable<any[]> {
    return collectionViewer.viewChange.pipe(map(() => []));
  }

  disconnect() {
    //
  }
}

class FakeDataSource extends DataSource<TestData> {
  _dataChange = new BehaviorSubject<TestData[]>([]);
  set data(data: TestData[]) {
    this._dataChange.next(data);
  }

  get data() {
    return this._dataChange.getValue();
  }

  constructor() {
    super();
    for (let i = 0; i < 4; i++) {
      this.addData();
    }
  }

  connect(): Observable<TestData[]> {
    return this._dataChange;
  }

  disconnect() {
    //
  }

  addData() {
    const nextIndex = this.data.length + 1;

    const copiedData = this.data.slice();
    copiedData.push({
      a: `a_${nextIndex}`,
      b: `b_${nextIndex}`,
      c: `c_${nextIndex}`,
    });

    this.data = copiedData;
  }
}

export class TableDataSource extends DataSource<any> {
  /** Stream of data that is provided to the table. */

  public data = new BehaviorSubject<[]>([]);

  constructor(items) {
    super();
    this.data = items;
  }

  getData() {
    return this.data;
  }

  /** Connect function called by the table to retrieve one stream containing the data to render. */
  connect(): Observable<[]> {
    return this.data;
  }

  disconnect() {}
}

/**
 * Data source for the DataTable view. This class should
 * encapsulate all logic for fetching and manipulating the displayed data
 * (including sorting, pagination, and filtering).
 */
export class DataTableDataSource extends DataSource<Tasks> {
  public data: Tasks[];
  paginator: MatPaginator | undefined;
  sort: MatSort | undefined;

  constructor() {
    super();
  }

  /**
   * Connect this data source to the table. The table will only update when
   * the returned stream emits new items.
   * @returns A stream of the items to be rendered.
   */
  connect(): Observable<Tasks[]> {
    if (this.paginator && this.sort) {
      // Combine everything that affects the rendered data into one update
      // stream for the data-table to consume.
      return merge(observableOf(this.data), this.paginator.page, this.sort.sortChange)
        .pipe(map(() => {
          if(this.data != undefined)
            return this.getPagedData(this.getSortedData([...this.data ]));
        }));
    } else {
      throw Error('Please set the paginator and sort on the data source before connecting.');
    }
  }

  /**
   *  Called when the table is being destroyed. Use this function, to clean up
   * any open connections or free any held resources that were set up during connect.
   */
  disconnect(): void {}

  /**
   * Paginate the data (client-side). If you're using server-side pagination,
   * this would be replaced by requesting the appropriate data from the server.
   */
  private getPagedData(data: Tasks[]): Tasks[] {
    if (this.paginator) {
      const startIndex = this.paginator.pageIndex * this.paginator.pageSize;
      return data.splice(startIndex, this.paginator.pageSize);
    } else {
      return data;
    }
  }

  /**
   * Sort the data (client-side). If you're using server-side sorting,
   * this would be replaced by requesting the appropriate data from the server.
   */
  private getSortedData(data: Tasks[]): Tasks[] {
    if (!this.sort || !this.sort.active || this.sort.direction === '') {
      return data;
    }

    return data.sort((a, b) => {
      const isAsc = this.sort?.direction === 'asc';
      switch (this.sort?.active) {
        case 'Status': return compare(a.Status, b.Status, isAsc);
        case 'Priority': return compare(a.Priority, b.Priority, isAsc);
        case 'Difficulty': return compare(a.Difficulty, b.Difficulty, isAsc);
        case 'SprintNumber': return compare(a.SprintNumber, b.SprintNumber, isAsc);
        case 'Id': return compare(a.Id, b.Id, isAsc);
        case 'Title': return compare(a.Title, b.Title, isAsc);
        case 'WorkDone': return compare(a.WorkDone, b.WorkDone, isAsc);
        case 'Assignee': return compare(a.Assignee, b.Assignee, isAsc);
        default: return 0;
      }
    });
  }
}

@Input()
  dataSource: DataSource<Expense>;