Angular5 Need function to check/uncheck mat-checkbox inside mat-table

Question

I can get checkboxes within the table to emit changes on check/uncheck, but am having troubles reciprocating when clicking on map pins to toggle checkbox states.

my table with map

Here's my table:

      <mat-table [dataSource]="dataSource">
        <ng-container matColumnDef="number">
          <mat-header-cell *matHeaderCellDef> Number </mat-header-cell>
          <mat-cell *matCellDef="let stock">
            // #myCheckbox needs to be unique
            <mat-checkbox #myCheckbox [checked] (change)="selectStock(stock, $event)"></mat-checkbox> <a href="">{{ stock.number }}</a>
          </mat-cell>
        </ng-container>
        <mat-header-row *matHeaderRowDef="displayedColumns"></mat-header-row>
        <mat-row *matRowDef="let row; columns: displayedColumns;" (click)="clickRow(row._id,$event)"></mat-row>
      </mat-table>

Then from my map, when you click on a pin, run some function

  (click)="someFunction(myCheckbox)"

In my class

    @ViewChild('myCheckbox') private myCheckbox: MatCheckbox;

    someFunction(myCheckbox){
         if (stock.isChecked) {
            this.myCheckbox.checked = false;
            } else {
            this.myCheckbox.checked = true;
         }
    }

This is the example I'm working off of but it's applying the same #id to each checkbox so only the first checkbox gets toggled (I'm assuming I need unique a unique id for each checkbox?)

Angular mat-checkbox getElementById

Is there any chance you still have your selectStock function code? — Benjamin Salerno
– Benjamin Salerno, Commented Oct 6, 2021 at 22:45

mduve · Accepted Answer · 2018-01-04 06:07:35Z

8

After more searching on the site, I was able to fix the issue using ViewChildren

Angular 4: setting the local variable # dynamically

angular4 local variable issue for *ngFor

      @ViewChildren('myCheckbox') private myCheckboxes : QueryList<any>;


      someFunction(item, index){

          let myCheckboxes = this.myCheckboxes.toArray();

          if (item.isChecked) {
              myCheckboxes[index].checked = true;
          } else {
              myCheckboxes[index].checked = false;
          }

      }

Good Stuff

edited Jan 4, 2018 at 6:07

answered Jan 4, 2018 at 5:59

mduve

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2 Comments

Adrian Baginski Over a year ago

go for myCheckboxes[index].checked = item.isChecked; , saves some lines of code :)

Code Guru Over a year ago

but this does not reflect on UI.. it still shows checked in the box

Torsten Barthel · Accepted Answer · 2018-07-31 09:34:15Z

A full, working example is following. In the class implementation TypeScript-File:

import { Component, OnInit, Inject, EventEmitter, Output, OnDestroy, QueryList, ViewChildren } from '@angular/core';

...    

export class YourClassName implements OnInit, OnDestroy {

    ...

    selectables : Array<string> = ['ah','be','ce'];
    @ViewChildren('checkboxMultiple') private checkboxesMultiple : QueryList<any>;

    ...

    selectionChange( event ) : void {

        // get index from template loop or so. In this case the value
        // of the mat-checkbox is an Array with the value as first and
        // the loop index as second entry
        let index = event.source.value[1];
        let checkboxesArray = this.checkboxesMultiple.toArray();
        checkboxesArray[index].checked = false;

        // You could also loop over all checkboxes and check/uncheck
        // them based on your logic
    }
}

And inside your template file:

...

<mat-checkbox #checkboxMultiple
        *ngFor="let selectable of selectables; let i = index"
        (change)="selectionChange($event)"
        [value]="[selectable, i]">
        {{ selectable }}&nbsp;&nbsp;
</mat-checkbox>

I found that you have to use the toArray() method of QueryList object to get the actual array of checkboxes.

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