Reactive forms - disabled attribute

Question

I have been using [attr.disabled] because I still like this template driven than programmatic enable()/disable() as it is superior IMO.

Change

<md-input formControlName="id" placeholder="ID" [disabled]="true"></md-input>

to

<md-input formControlName="id" placeholder="ID" [attr.disabled]="true"></md-input>

If you are on newer material change md-input to mat-input.

In my case with Angular 8. I wanted to toggle enable/disable of the input depending on the condition.

[attr.disabled] didn't work for me so here is my solution.

I removed [attr.disabled] from HTML and in the component function performed this check:

if (condition) {
    this.form.controls.myField.disable();
} else {
    this.form.controls.myField.enable();
}

You can enable/disable a form control by using the following methods:

control.disable() or control.enable()

If that did not work for you can use a directive

import { NgControl } from '@angular/forms';

@Directive({
  selector: '[disableControl]'
})
export class DisableControlDirective {

  @Input() set disableControl( condition : boolean ) {
    const action = condition ? 'disable' : 'enable';
    this.ngControl.control[action]();
  }

  constructor( private ngControl : NgControl ) {
  }

}

Then you could use it like this

<input [formControl]="formControl" [disableControl]="disable">
<button (click)="disable = true">Disable</button>
<button (click)="disable = false">Enable</button>

This technique is described here:

https://netbasal.com/disabling-form-controls-when-working-with-reactive-forms-in-angular-549dd7b42110

Hope it helps

I found that I needed to have a default value, even if it was an empty string. So this:

this.registerForm('someName', {
  firstName: new FormControl({disabled: true}),
});

...had to become this:

this.registerForm('someName', {
  firstName: new FormControl({value: '', disabled: true}),
});

See my question (which I don't believe is a duplicate): Passing 'disabled' in form state object to FormControl constructor doesn't work