title: Angular 6 - How to format [ngClass] when using a variable
body: <p>I want to add a class based on an item in an object within my components typescript file. I can't seem to get the format correct for this to work.</p>
  
  <p>When the 'selectedColourPalette' value is greater than zero, I want to add the primary colour from 'colourPaletteOne' into the HTML.</p>
  
  <p><strong>CSS</strong></p>
  
  <pre><code>colourPaletteOne = {
      primary: 'blue', 
      secondary: 'grey',    
    }
  </code></pre>
  
  <p><strong>HTML</strong></p>
  
  <pre><code>&lt;div&gt; [ngClass]="{'border-{{colourPaletteOne.primary}}' : selectedColourPalette &gt; 0}"&gt;&lt;/div&gt;
  </code></pre>