mat-checkbox仅在条件为真时检查

Question

I have a user table list with mat-checkbox . When mat-checkbox is clicked, the checkbox should be checked only if a certain condition is true.

Here in this code, I am trying to have checkbox checked only for id=2 . But as you can see, initially when checkbox of 2 is clicked, it doesn't get checked even though 2 is added to array of elements which should be checked.

On the other hand, when checkbox of 1,3 or 4 is clicked, they get checked.

component.html

<tbody>
    <tr *ngFor="let user of users; let in = index">
            <td>
                <mat-checkbox [ngModel]="canbeChecked(user.id)" (click)="userSelectClick(user.id)"></mat-checkbox>
            </td>
    </tr>
</tbody>

component.ts

export class AppComponent {

  users = [{ id: 1 }, { id: 2 }, { id: 3 }, { id: 4 }];
  checked: boolean = true
  constructor() { }
  selected: any = [];

  canbeChecked(id): boolean {
    console.log("check " + id)
    console.log(this.selected)
    return this.selected.includes(id);

  }

  userSelectClick(id) {

    if (!this.selected.includes(id)) {
      if (id == 2)
        this.selected.push(id);
      console.log("select " + id)
      console.log(this.selected)
    }
    else {
      this.selected = this.selected.filter(item => item !== id)
    }

  }

}

Working code: https://stackblitz.com/edit/mat-checkbox-conditional

Answer 1

I have used event binding on ngModel in the html and also modified some code in app.component.ts. Now only the checkbox with id 2 can be checked. Please see the code below

in app.component.html

<mat-checkbox (ngModel)="canbeChecked(user.id)" (click)="userSelectClick(user.id)"></mat-checkbox>

and in app.component.ts

export class AppComponent {

  users = [{ id: 1 }, { id: 2 }, { id: 3 }, { id: 4 }];
  checked: boolean = true
  constructor() { }
  selected: any = [];

  canbeChecked(id): boolean {
    console.log(this.selected.includes(id));
    return this.selected.includes(id);
  }

  userSelectClick(id) {

    if (!this.selected.includes(id)) {
      if (id == 2){
         this.selected.push(id);
      }
      else{
         return false;
      }
    }
    else {
      if(id == 2){
        this.selected = [];
      }
      else
       return false;
    }
  }

}

Here is a working link

https://stackblitz.com/edit/mat-checkbox-conditional-z8uc94

Answer 2

I'm novice over stackoverflow.You can try change event for that stuff.

component.ts

import { Component } from '@angular/core';


@Component({
  selector: 'material-app',
  templateUrl: 'app.component.html',
  styleUrls: ['app.component.css']
})
export class AppComponent {
user_checked = false;
  users = [{ id: 1 }, { id: 2 }, { id: 3 }, { id: 4 }];
  checked: boolean = false;
  constructor() { }
  selected: any = [];

  canbeChecked(id): boolean {
    console.log("check " + id)
    console.log(this.selected)
    return this.selected.includes(id);

  }

  userSelectClick(event,id) {
    if (!this.selected.includes(id)) {
      if (id == 2)
        this.selected.push(id);
      console.log("selecrted iDs " + id)
      console.log(this.selected)
    }
    else {
      this.selected = this.selected.filter(item => item !== id)
    }
  }

}

/**
 * Copyright Google LLC All Rights Reserved.
 *
 * Use of this source code is governed by an MIT-style license that can be
 * found in the LICENSE file at https://angular.io/license
 */

component.html

Checkboxes