title: How to set Angular2 component input conditionally?
body: <p>Consider the following case.</p>
  
  <p>Parent component:</p>
  
  <pre><code>&lt;div title="title1"&gt;
    &lt;my-component input="title2"&gt;&lt;/my-component&gt;
    &lt;my-component&gt;&lt;/my-component&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p>MyComponent:</p>
  
  <pre><code>&lt;div [title]="input"&gt;ABC&lt;/div&gt;
  </code></pre>
  
  <p>The problem here is that first "ABC" div will have the <code>"title2"</code> tooltip while the second one will have whatever MyComponent has as default value for <code>input</code>, and this will "override" <code>"title1"</code> tooltip which is not desired.</p>
  
  <p>How can I avoid setting "title" in MyComponent template if no "input" is received?</p>