angularjs very simple yes/no boolean select directive not binding
<p>I'm trying to write what must be the simplest angular directive which displays a Yes/No select list and is bound to a model containing a boolean value. Unfortunately the existing value is never preselected. My directive reads</p>

<pre><code>  return {
        restrict: 'E',
        replace: true,
        template: '&lt;select class="form-control"&gt;&lt;option value="true"&gt;Yes&lt;/option&gt;&lt;option value="false"&gt;No&lt;/option&gt;&lt;/select&gt;',
        scope: {
              ngModel: '='
        }
  }
</code></pre>

<p>and I am calling the directive as</p>

<pre><code>&lt;yesno ng-model="brand.is_anchor"&gt;&lt;/yesno&gt;
</code></pre>

<p>The select options display and the generated HTML reads as</p>

<pre><code>&lt;select class="form-control ng-isolate-scope ng-valid" ng-model="brand.is_anchor"&gt;
    &lt;option value="? boolean:false ?"&gt;&lt;/option&gt;
    &lt;option value="true"&gt;Yes&lt;/option&gt;
    &lt;option value="false"&gt;No&lt;/option&gt;
&lt;/select&gt;
</code></pre>

<p>The initial value of the bound model is "false" but it always displays an empty option and per the first option listed in the generated HTML.</p>

<p>Can anybody please advise?</p>