title: best way to trigger AngularJS ng-show
body: <p>I'm building an autocomplete box in AngularJS. The relevant code looks like this</p>
  
  <pre><code>&lt;input type="text" ng-model="tag"&gt;
  &lt;div ng-show="tag"&gt;
    &lt;ul&gt;
      &lt;li ng-repeat="t in user.tags | filter:{name:tag}"&gt;
        &lt;a&gt;{{t.name}}&lt;/a&gt;
      &lt;/li&gt;
    &lt;/ul&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p>I'd like to know what is the best way to show the list of suggestions when "tag" has no value (i.e. I want to show all the tags when the user press the down key. No need to mention the keypressing code on the answer).</p>