Cannot assign to 'value' because it is a constant or a read-only property. Angular 6

angular form-control
Abx picture Abx · Aug 2, 2018 · Viewed 13.8k times · Source

I am trying to set a value to a Mat input using FormControl

<input name="contact" matInput [matAutocomplete]="contactAuto"  [formControl]="myControl" #contact (blur)="validateInput($event, contact.value)"  >

In my Ts

myControl = new FormControl();
this.myControl.value = 'contact';

The above code is working fine but I get an error 

Cannot assign to 'value' because it is a constant or a read-only property

Am I missing something here?

Answer

rpeshkov picture rpeshkov · Aug 2, 2018

It's not allowed to set value like you are trying. You need to either use setValue or patchValue methods.

https://angular.io/api/forms/FormControl#setvalue

https://angular.io/api/forms/FormControl#patchvalue

For FormControl they're identical, but those methods work differently for i.e. FormGroup.

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