title: filter and unfilter on ng-click with buttons
body: <p>hello i have a couple of buttons i want to filter data with, but i can't figure out how to make it unfilter when i click the button again.  I use the normal filtering expression like:</p>
  
  <pre><code>&lt;tr ng-repeat='ledata in datas  |  filter:thecondition'&gt;&lt;/tr&gt;
  </code></pre>
  
  <p>where the thecondition may vary depending on the button clicked, the button's code is the following</p>
  
  <pre><code>ng-click="thecondition = {type: 1}"
  </code></pre>
  
  <p>also how can i mark it with ng-class? make the button look pressed? thanks.</p>