How to select all checkboxes in Angular with ngFor and ngIf?

Question

I would like to select all the checkboxes in Angular, where I have ngFor and ngIf when activating "Seleccionar todo (Select all)" and all the checkboxes of months are activated. The months are stored in an array.

HTML representation

<div class="form-group row">
     <label class="col-2 col-form-label">Meses de siembra</label>
         <div class="col-8">
             <table>
                 <tr>
                     <label>
                         <input type="checkbox" ng-model name="seleccionarTodo"> Seleccionar todo
                     </label>
                 </tr>
                 <tr>
                     <td>
                         <div *ngFor="let m of mesesSiembra; let i=index">
                             <label *ngIf="i<6">
                             <input type="checkbox" ng-model name="mes1a6"> {{m.nombre}}
                             </label>
                         </div>
                     </td>
                     <td>
                         <div *ngFor="let m of mesesSiembra; let i=index">
                             <label *ngIf="i>5">
                                 <input type="checkbox" ng-model name="mes7a12"> {{m.nombre}}
                             </label>
                         </div>
                     </td>
                 </tr>
             </table>
         </div>
</div>

Answer 1

Each m in mesesSiembra will need to have a boolean property representing the checked state of the checkbox and bind it with [checked]="m.checked" and (click)="m.checked = !m.checked". You will also needto have a unique name for each form element so use the index to make the name unique [name]="'mes_' + i".

To check them all you have a function that does

this.mesesSiembra = this.mesesSiembra.map(m => ({ ...m, checked: true }));

Here is a demo https://stackblitz.com/edit/angular-ivy-ibqzjj?file=src%2Fapp%2Fapp.component.html