title: Dynamically Show/hide directive
body: <p>I am trying to implement some directive, which will be based on the value of one variable in other Service. Here is my code:</p>
  
  <pre><code>        if (this.SomeService.variable.condition){
              element.show();
          } else {
              element.hide();
          };
  </code></pre>
  
  <p>However, it is called only once, when the page is bootstraped. How can I make it so that if the variable changes, the element shows/hides? Is there any way to do it without watcher?</p>