ion:</em> Interpolation attributes are assigned to the attribute object
allowing other directives to read the interpolated value.</p>
</li>
<li><p><em>Observing interpolated attributes:</em> Use <code>$observe</code> to observe the value changes of attributes
that contain interpolation (e.g. <code>src=&quot;{{bar}}&quot;</code>). Not only is this very efficient but it&#39;s also
the only way to easily get the actual value because during the linking phase the interpolation
hasn&#39;t been evaluated yet and s