title: Angular Material use the checked status of checkbox as a readonly basis of other control in form group
body: <p>I'm new on angular and I wanted to use the checked status of the checkbox as basis on the readonly property of textarea. </p>
  
  <pre><code>&lt;div fxlayout="row" fxLayoutAlign="center center" *ngFor="let test of cosmetriTests.controls; let i=index" [formGroupName]="i"&gt;
   &lt;mat-form-field class="w-25-p" appearance="outline" &gt;
        &lt;textarea [id]="'actualCoaField_'+i"
            matInput
            formControlName="actual_coa_qualifier"
            (keyup) = "evaluateCoa()"
            [readonly] = "test.checked.include==false"
            required&gt;
        &lt;/textarea&gt;
   &lt;/mat-form-field&gt;
  
   &lt;mat-checkbox
       formControlname="include"
       [checked]="true"
       [required]="true"
   &lt;/mat-checkbox&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p>Thank you in advance guys.</p>