title: In angular.js, what does an ampersand in the directive mean?
body: <p>In this code:</p>
  
  <pre><code>app.directive( 'myCustomDirective', function() {
    return {
      restrict: 'EA',
      scope: { value: '=myCustomDirective', clickable: '&amp;', editing: '=' },
      template: '&lt;span ng-click="handleClick()" ng-bind="value"&gt;&lt;/span&gt;',
      ...
  </code></pre>
  
  <p>What does <code>clickable: '&amp;'</code> denote? </p>
  
  <p>When I do find Angular documentation, I cannot understand it.  It seems to be written in a catch-22 code that can be understood only by  people who already understand what is being explained. </p>
  
  <p>For example, I found <a href="http://www.youtube.com/watch?v=mZGgNPTHc2Q" rel="noreferrer">this video</a>, which apparently explains the &amp; thing, but  he may as well have been speaking Mandarin. </p>