title: Filter ng-options from ng-options selection
body: <p>I'm hoping to solve three problems... </p>
  
  <p>In my app page I have one select for states and another for counties.  For states I have:</p>
  
  <pre><code>&lt;select ng-model="filter.stateID" ng-options="item.stateID as item.state for item in st_option"&gt;
  &lt;/select&gt;
  </code></pre>
  
  <p><strong>Data:</strong></p>
  
  <pre class="lang-js prettyprint-override"><code>[
    { state="California", stateID="5"},
    { state="Arizona", stateID="3"},
    { state="Oregon", stateID="38"},
    { state="Texas", stateID="44"},
    { state="Utah", stateID="45"},
    { state="Nevada", stateID="29"}
  ]
  </code></pre>
  
  <p>For my County select I have:</p>
  
  <pre><code>&lt;select ng-model="filter.countyID" ng-options="item.countyID as item.county for item in co_option"&gt;
   &lt;/select&gt;
  </code></pre>
  
  <p><strong>Data:</strong></p>
  
  <pre class="lang-js prettyprint-override"><code>[
    { county="Orange", countyID="191", co_state_id="5"},
    { county="Multiple Counties", countyID="3178", co_state_id="3"},
    { county="Sonoma", countyID="218", co_state_id="38"},
    { county="Los Angeles", countyID="190", co_state_id="44"}
  ]
  </code></pre>
  
  <p>This is my <code>ng-repeat</code>:</p>
  
  <pre><code>&lt;div ng-repeat="project in projects | filter:filter"&gt;
      &lt;div&gt;
          State: {{project.state}}&lt;br&gt; 
          County: {{project.county}}&lt;br&gt;
          &lt;span ng-hide="{{project.stateID}}"&gt;&lt;/span&gt;
          &lt;span ng-hide="{{project.countyID}}"&gt;&lt;/span&gt;
      &lt;/div&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p>So, as you can see I'm using the <code>stateID</code> on the state select and on the county select I have the corresponding state id set in <code>co_state_id</code> in the county data set.</p>
  
  <p>I'd like to do a few things:</p>
  
  <ol>
  <li>Hide the county select until a state is selected.</li>
  <li>After a state is selected, filter the county select options by the selected <code>stateID</code> / <code>co_state_id</code></li>
  <li>Filter the <code>ng-repeat</code> by first the <code>stateID</code>, then by the <code>countyID</code>.</li>
  </ol>
  
  <p>I also haven't see a way to set <code>filter.stateID</code> to <code>true</code> or filter by a number instead of a string.  when I filter by stateID I get mixed results because some <code>stateID</code>'s can have "1" in them..</p>