Angular Mat-Paginator Not Working with Parent to Child Passing DataSource? Here’s the Solution!

Are you struggling to get your Angular mat-paginator to work with parent-to-child data source passing? You’re not alone! This is a common issue many developers face when trying to implement pagination in their Angular applications. In this article, we’ll dive into the solution and provide a step-by-step guide on how to fix this problem. So, let’s get started!

What’s the Problem?

When you try to pass a data source from a parent component to a child component using the `@Input()` decorator, the mat-paginator doesn’t seem to work as expected. The paginator appears, but it doesn’t respond to changes in the data source, and the pagination controls don’t update correctly. This is frustrating, especially when you’ve spent hours setting up your data source and pagination logic.

The Reason Behind the Issue

The problem lies in the way Angular handles changes to the data source. When you pass a data source from a parent component to a child component, Angular doesn’t automatically detect changes to the data source. This means that the mat-paginator doesn’t receive the updated data source, resulting in the pagination controls not working correctly.

The Solution

To fix this issue, you need to manually notify the mat-paginator about changes to the data source. You can do this by using the `ChangeDetectorRef` from the `@angular/core` module. Here’s an example of how to implement this solution:

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

@Component({
  selector: 'app-child',
  template: `
    <mat-paginator [pageSizeOptions]="[5, 10, 25]" showFirstLastButtons></mat-paginator>
    <mat-table [dataSource]="dataSource">
      <ng-container matColumnDef="column1">
        <mat-header-cell *matHeaderCellDef> Column 1 </mat-header-cell>
        <mat-cell *matCellDef="let element"> {{ element.column1 }} </mat-cell>
      </ng-container>
      <mat-header-row *matHeaderRowDef=" ['column1']"></mat-header-row>
      <mat-row *matRowDef="let row; columns: ['column1']"></mat-row>
    </mat-table>
  `,
})
export class ChildComponent {
  @Input() dataSource: MatTableDataSource<any>;

  constructor(private cdr: ChangeDetectorRef) { }

  ngAfterViewInit() {
    this.cdr.detectChanges();
  }
}

In this example, we’ve added the `ChangeDetectorRef` to the child component’s constructor and called the `detectChanges()` method in the `ngAfterViewInit()` lifecycle hook. This notifies the mat-paginator about changes to the data source, ensuring that it updates correctly.

Step-by-Step Implementation

Here’s a step-by-step guide on how to implement this solution in your Angular application:

1. Create a new Angular component for the child component:

   ng generate component child

2. Add the `MatPaginatorModule` and `MatTableModule` to your module imports:

   import { MatPaginatorModule, MatTableModule } from '@angular/material';
       @NgModule({
         imports: [
           MatPaginatorModule,
           MatTableModule,
         ],
       })

3. Add the `ChangeDetectorRef` to your child component’s constructor:

   import { ChangeDetectorRef } from '@angular/core';
       constructor(private cdr: ChangeDetectorRef) { }

4. Call the `detectChanges()` method in the `ngAfterViewInit()` lifecycle hook:

   ngAfterViewInit() {
         this.cdr.detectChanges();
       }

5. Pass the data source from the parent component to the child component using the `@Input()` decorator:

   <app-child [dataSource]="dataSource"></app-child>

6. Update the mat-paginator template to use the passed data source:

   <mat-paginator [pageSizeOptions]="[5, 10, 25]" showFirstLastButtons></mat-paginator>

Troubleshooting Tips

If you’re still experiencing issues with the mat-paginator, here are some troubleshooting tips to help you resolve the problem:

• Verify that the data source is being passed correctly from the parent component to the child component.

• Check that the `ChangeDetectorRef` is being called correctly in the `ngAfterViewInit()` lifecycle hook.

• Ensure that the mat-paginator is correctly configured and that the `pageSizeOptions` property is set correctly.

• Try setting the `dataSource` property directly on the mat-paginator component instead of passing it as an `@Input()` property.

Conclusion

In this article, we’ve explored the common issue of the Angular mat-paginator not working with parent-to-child data source passing. We’ve provided a step-by-step guide on how to fix this problem using the `ChangeDetectorRef` and `ngAfterViewInit()` lifecycle hook. By following these instructions, you should be able to get your mat-paginator working correctly with your data source.

Remember to troubleshoot any issues that may arise during implementation, and don’t hesitate to reach out if you need further assistance. Happy coding!

Keyword	Description
Angular	A JavaScript framework for building web applications.
Mat-Paginator	A pagination component from the Angular Material library.
ChangeDetectorRef	A service from the Angular core module that detects changes to the component tree.
ngAfterViewInit	A lifecycle hook that is called after the component’s view has been initialized.

By following the instructions in this article, you should be able to resolve the issue of the Angular mat-paginator not working with parent-to-child data source passing. Remember to troubleshoot any issues that may arise during implementation, and don’t hesitate to reach out if you need further assistance. Happy coding!

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