Refreshing an Angular Material Table Data Source: Example Code

• Angular: A JavaScript framework for building dynamic web applications.
• Angular Material: A collection of UI components built on top of Angular that provide a consistent and Material Design-inspired look and feel.
• mat-table: An Angular Material component specifically designed for displaying tabular data.
• DataSource: An interface or class that defines how data is provided to the mat-table. It can be an array of data, an Observable (a stream of data), or a custom implementation.

The Refreshing Process:

2. Triggering MatTable Refresh:

   • renderRows() Method: The most direct approach is to call the renderRows() method of the mat-table component. This method instructs the table to re-render its content based on the updated DataSource.
   • Paginator Trick: If you're using the MatPaginator component for pagination, you can leverage a clever trick. Call the _changePageSize() method of the paginator instance, passing the current page size. This essentially forces a refresh without actually changing the page size. However, it's important to note that _changePageSize() is an internal method and might not be publicly accessible in future versions of Angular Material. Use it with caution and explore alternative methods if necessary.

Key Points:

• Choose the refresh method that best suits your application's needs and complexity.
• If using _changePageSize(), be aware of its internal nature and potential future changes.
• Observables offer a more robust approach for handling asynchronous data updates.

Refreshing an Angular Material Table Data Source: Example Code

Using renderRows() Method:

import { Component, OnInit, ViewChild } from '@angular/core';
import { MatTableDataSource } from '@angular/material/table';

interface MyData {
  name: string;
  age: number;
}

@Component({
  selector: 'app-my-table',
  templateUrl: './my-table.component.html',
  styleUrls: ['./my-table.component.css']
})
export class MyTableComponent implements OnInit {
  dataSource = new MatTableDataSource<MyData>();
  displayedColumns: string[] = ['name', 'age'];

  @ViewChild('table') table: MatTable<MyData>;

  ngOnInit() {
    this.dataSource.data = [
      { name: 'John Doe', age: 30 },
      { name: 'Jane Doe', age: 25 }
    ];
  }

  refreshData() {
    // Simulate data update
    this.dataSource.data.push({ name: 'New User', age: 40 });
    this.table.renderRows(); // Trigger table refresh
  }
}

In this example:

• We have a MyData interface defining the data structure.
• The dataSource is initialized as a MatTableDataSource<MyData>.
• The refreshData() method simulates adding a new item to the data source.
• Finally, we call table.renderRows() to instruct the table to re-render with the updated data.

Using Observables (Optional):

import { Component, OnInit } from '@angular/core';
import { MatTableDataSource } from '@angular/material/table';
import { BehaviorSubject, Observable } from 'rxjs';
import { mergeMap } from 'rxjs/operators';

interface MyData {
  name: string;
  age: number;
}

@Component({
  selector: 'app-my-table',
  templateUrl: './my-table.component.html',
  styleUrls: ['./my-table.component.css']
})
export class MyTableComponent implements OnInit {
  dataSource = new MatTableDataSource<MyData>();
  displayedColumns: string[] = ['name', 'age'];

  private dataSubject = new BehaviorSubject<MyData[]>([]);
  data$: Observable<MyData[]>;

  ngOnInit() {
    this.data$ = this.dataSubject.asObservable();
    this.dataSubject.next([
      { name: 'John Doe', age: 30 },
      { name: 'Jane Doe', age: 25 }
    ]);
  }

  refreshData() {
    // Simulate data update
    this.dataSubject.next([...this.dataSubject.getValue(), { name: 'New User', age: 40 }]);
  }
}

Here, we leverage Observables:

• A BehaviorSubject holds the current data (dataSubject).
• An Observable (data$) is derived from the BehaviorSubject.
• In the DataSource's connect() method (not shown here), you'd use Observable.merge() to combine data$ with any sort/pagination observables.
• The refreshData() method updates the BehaviorSubject, triggering a new emission and consequently refreshing the table.

• If you have a simple data structure and updates are infrequent, you can directly update the dataSource.data property after making changes. This triggers a re-render automatically.

Leveraging Change Detection Strategy (OnPush):

• By setting the changeDetection strategy to OnPush in your component (using the ChangeDetectionStrategy enum), Angular will only re-render the table when changes are detected in the dataSource object itself. This can be more performant for large datasets.
  • Make sure to update the data source object reference (e.g., by creating a new array with updated data) instead of mutating the existing array directly.

Custom Logic in connect() Method:

• The connect() method of your custom DataSource implementation offers more control over data updates. You can implement logic here to check for data changes and trigger a refresh.

Third-Party Libraries:

• Libraries like ngx-datatable or @angular/cdk/collections might provide additional functionalities for data source management and refreshing.

Choosing the Right Method:

• The best approach depends on several factors:
  • Complexity of your data structure
  • Frequency of data updates
  • Performance requirements
  • Preference for a reactive or imperative approach

Here's a summary table: