Using Angular, create mat-checkbox components that are dynamically generated and bound using

Question

Using Angular, create mat-checkbox components that are dynamically generated and bound using

In my Offer class, I have a property called "units" which is an array of objects.

export class Offer {
   public propertyA: string;
   public propertyB: string;
   public units: Unit[];
}

export class Unit {    
    public code: string,
    public name: string,
    public checked: boolean
}

I am developing with Angular 2 and want to display these units as selectable checkboxes for the user. I am also utilizing angular material components.

The HTML implementation looks like this:

<div *ngFor="let unit of model.units; let i=index">
  <mat-checkbox [(ngModel)]="model.units[i].checked"
    id="units[{{i}}]" name="units[{{i}}]">
       {{ unit.name }}
  </mat-checkbox>                        
</div>

To load the units property, I use the following:

this.model.units.push(new Unit("code1","name1", false));
this.model.units.push(new Unit("code2","name2", false));
this.model.units.push(new Unit("code3","name3", false));

However, when I submit the form, the checked property does not retain the selected values. What could be causing this issue?

angular typescript angular-material

Answer 1

Answer №1

To implement one-way binding, add [checked]="unit.checked" and remove ngModel, id and name attributes from your mat-checkbox.

If you want to achieve two-way binding, you can follow a similar approach used in this example:

In your HTML file:

<div *ngFor="let unit of model.units">
  <mat-checkbox [checked]="unit.checked" 
  (change)="valueChange(model.units, unit, $event)">
       {{ unit.name }}
  </mat-checkbox>                        
</div>

Add the following method to your component file:

valueChange(model.units, unit, $event) {
        // set the two-way binding for the specific unit with the event
        model.units[unit].checked = $event.checked;
    }

UPDATE: To enable two-way binding without explicit handling, ensure that each item in model.units has a checked property.

In your component file:

this.model.units.forEach(item => {
                       item.checked = false; // adjust as needed
                    });

In your HTML file:

 <div *ngFor="let unit of model.units; let i=index">
    <mat-checkbox [(ngModel)]="unit.checked" [checked]="unit.checked"                                                                                    
    name="{{i}}-name">                             
    </mat-checkbox>
</div>

If you also want to control the enable/disable options, you can add the following:

In your component file:

this.model.units.forEach(item => {
                       item.checked = false; // adjust as needed
                       item.disabled = true; // adjust as needed
                    });

In your HTML file:

<div *ngFor="let unit of model.units; let i=index">
        <mat-checkbox [(ngModel)]="unit.checked" [checked]="unit.checked"
         [disabled]="unit.disabled"                                                                                    
       name="{{i}}-name">
        </mat-checkbox>
    </div>

Answer 2

To implement one-way binding, add [checked]="unit.checked" and remove ngModel, id and name attributes from your mat-checkbox.

If you want to achieve two-way binding, you can follow a similar approach used in this example:

In your HTML file:

<div *ngFor="let unit of model.units">
  <mat-checkbox [checked]="unit.checked" 
  (change)="valueChange(model.units, unit, $event)">
       {{ unit.name }}
  </mat-checkbox>                        
</div>

Add the following method to your component file:

valueChange(model.units, unit, $event) {
        // set the two-way binding for the specific unit with the event
        model.units[unit].checked = $event.checked;
    }

UPDATE: To enable two-way binding without explicit handling, ensure that each item in model.units has a checked property.

In your component file:

this.model.units.forEach(item => {
                       item.checked = false; // adjust as needed
                    });

In your HTML file:

 <div *ngFor="let unit of model.units; let i=index">
    <mat-checkbox [(ngModel)]="unit.checked" [checked]="unit.checked"                                                                                    
    name="{{i}}-name">                             
    </mat-checkbox>
</div>

If you also want to control the enable/disable options, you can add the following:

In your component file:

this.model.units.forEach(item => {
                       item.checked = false; // adjust as needed
                       item.disabled = true; // adjust as needed
                    });

In your HTML file:

<div *ngFor="let unit of model.units; let i=index">
        <mat-checkbox [(ngModel)]="unit.checked" [checked]="unit.checked"
         [disabled]="unit.disabled"                                                                                    
       name="{{i}}-name">
        </mat-checkbox>
    </div>

Answer 3

Answer №2

I have successfully tested this code in Angular 7.

It is important to ensure that each checkbox has a unique name.

<mat-grid-list cols="4" rowHeight="100px">
                    <mat-grid-tile *ngFor="let item of aspNetRolesClaims" [colspan]="1" [rowspan]="1">
                        <span>{{item.claimValue}}</span>
                        <mat-checkbox [(ngModel)]="item.claimValue" name="{{item.claimType}}">{{item.claimType}}</mat-checkbox>
                    </mat-grid-tile>
                </mat-grid-list>

Answer 4

I have successfully tested this code in Angular 7.

It is important to ensure that each checkbox has a unique name.

<mat-grid-list cols="4" rowHeight="100px">
                    <mat-grid-tile *ngFor="let item of aspNetRolesClaims" [colspan]="1" [rowspan]="1">
                        <span>{{item.claimValue}}</span>
                        <mat-checkbox [(ngModel)]="item.claimValue" name="{{item.claimType}}">{{item.claimType}}</mat-checkbox>
                    </mat-grid-tile>
                </mat-grid-list>

Answer 5

Answer №3

After testing in Angular 7, I did not encounter any errors related to your question. Feel free to check out a live demo on this StackBlitz example. Here is my response:

To ensure functionality, be sure to assign a unique name to the ngModel bound input.

Here's an example using your code snippet:

<div *ngFor="let unit of model.units; let i=index">
  <mat-checkbox 
    [(ngModel)]="model.units[i].checked"
    id="units-{{i}}" 
    name="units-{{i}}" // instead of array notation
  >
      {{ unit.name }}
  </mat-checkbox>                        
</div>

In personal practice, I avoid using array notation like units[{{i}}] as it can merge all fields together, although it doesn't seem to be causing issues in your current implementation.

Answer 6

After testing in Angular 7, I did not encounter any errors related to your question. Feel free to check out a live demo on this StackBlitz example. Here is my response:

To ensure functionality, be sure to assign a unique name to the ngModel bound input.

Here's an example using your code snippet:

<div *ngFor="let unit of model.units; let i=index">
  <mat-checkbox 
    [(ngModel)]="model.units[i].checked"
    id="units-{{i}}" 
    name="units-{{i}}" // instead of array notation
  >
      {{ unit.name }}
  </mat-checkbox>                        
</div>

In personal practice, I avoid using array notation like units[{{i}}] as it can merge all fields together, although it doesn't seem to be causing issues in your current implementation.

Answer 7

Answer №4

If you find yourself unable to utilize [(ngModel)] in situations where a FormGroup is employed, here's an alternative approach. In this scenario, it is assumed that 'obj' represents a custom object with an 'IsSelected' property.

<mat-checkbox [checked]="obj.IsSelected"                                      
 (change)="onSelectionChanged($event, obj)">{{obj.Name}}
</mat-checkbox>

To manually update the 'obj.IsSelected' property within the 'onSelectionChanged' method.

public onSelectionChanged(arg: MatCheckboxChange, obj:any) {
 obj.IsSelected = arg.checked;
}

Answer 8

If you find yourself unable to utilize [(ngModel)] in situations where a FormGroup is employed, here's an alternative approach. In this scenario, it is assumed that 'obj' represents a custom object with an 'IsSelected' property.

<mat-checkbox [checked]="obj.IsSelected"                                      
 (change)="onSelectionChanged($event, obj)">{{obj.Name}}
</mat-checkbox>

To manually update the 'obj.IsSelected' property within the 'onSelectionChanged' method.

public onSelectionChanged(arg: MatCheckboxChange, obj:any) {
 obj.IsSelected = arg.checked;
}

Answer 9

Answer №5

Here is an alternative approach that may offer a simplified solution. This method has been proven effective when used within a form group.

<form [formGroup]='formGroup'>
    <mat-checkbox [(ngModel)]="obj.IsSelected" [ngModelOptions]="{standalone:> true}">
        {{obj.Name}}
    </mat-checkbox>
</form>

Answer 10

Here is an alternative approach that may offer a simplified solution. This method has been proven effective when used within a form group.

<form [formGroup]='formGroup'>
    <mat-checkbox [(ngModel)]="obj.IsSelected" [ngModelOptions]="{standalone:> true}">
        {{obj.Name}}
    </mat-checkbox>
</form>

Using Angular, create mat-checkbox components that are dynamically generated and bound using

Answer №1

Answer №2

Answer №3

Answer №4

Answer №5

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