title: Why doesn't validation work after cleaning?
body: <p>After the adding method: "addPost", the form is cleared and the validation does not work and the add button is active,  it should be active only when the forms are correctly populated. Help please solve the problem</p>
  
  <p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
  <div class="snippet-code">
  <pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;div class="card" *ngIf="toggleCreate"&gt;
      &lt;div class="card-body"&gt;
          &lt;form [formGroup]="angForm" novalidate&gt;
              &lt;div class="form-group"&gt;
                  &lt;label class="col-md-4"&gt;Picture Title&lt;/label&gt;
                  &lt;input type="text" class="form-control" formControlName="title" minlength="1" #title/&gt;
              &lt;/div&gt;
              &lt;div *ngIf="angForm.controls['title'].invalid &amp;&amp; (angForm.controls['title'].dirty || angForm.controls['title'].touched)"
                   class="alert alert-danger"&gt;
                  &lt;div *ngIf="angForm.controls['title'].errors.required"&gt;
                      Title is required.
                  &lt;/div&gt;
              &lt;/div&gt;
              &lt;div class="form-group"&gt;
                  &lt;label class="col-md-4"&gt;Picture Address (url)&lt;/label&gt;
                  &lt;input type="url" class="form-control" formControlName="url" #url pattern="https?://.+"
                         title="Include http://"/&gt;
              &lt;/div&gt;
              &lt;div *ngIf="angForm.controls['url'].invalid &amp;&amp; (angForm.controls['url'].dirty || angForm.controls['url'].touched)"
                   class="alert alert-danger"&gt;
                  Address(url) is required.
                  &lt;div *ngIf="angForm.controls['url'].errors.required "&gt;
  
                  &lt;/div&gt;
              &lt;/div&gt;
              &lt;div class="form-group but-group"&gt;
                  &lt;button (click)="addPost(title.value, url.value); title.value=''; url.value=''"
                          [disabled]="angForm.pristine || angForm.invalid"
                          class="btn btn-primary"&gt;Add
                  &lt;/button&gt;
              &lt;/div&gt;
          &lt;/form&gt;
      &lt;/div&gt;
  &lt;/div&gt;</code></pre>
  </div>
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  </p>