title: PrimeNG: assigning the styleClass to p-column based on some condition
body: <p>I want to assign a <code>styleClass</code> to the <code>p-header</code> element of the <code>p-dataTable</code> based on a condition (only first five columns need a specific style).</p>
  
  <p>How can I achieve that? 
  I tried the following -</p>
  
  <pre><code>&lt;p-column 
      *ngFor = "let columnName of columns; let i = index;" 
      field="name" 
      styleClass="{{getStyleClass(i-1)}}"&gt;
  </code></pre>
  
  <p>and the <code>getStyleClass()</code> function in the <code>ts</code> file, but that doesn't seems to work.</p>