title: $scope passes as value in attrs while controller as returns string
body: <p>When values to directive is passed using $scope inside my link funciton I am able to access them using the variables attrs while if I pass values using controller as syntax I am able to access just the string as passed. Here is my code</p>
  
  <p>directive call</p>
  
  <pre><code>&lt;div linear-chart chart-data="salesData"&gt;&lt;/div&gt;&lt;/div&gt;
  &lt;div linear-chart2 chart-data="ctrl.salesData2"&gt;&lt;/div&gt;&lt;/div&gt; 
  </code></pre>
  
  <p>code for directive</p>
  
  <pre><code>app.directive('linearChart', function($window){
     return{
        restrict:'EA',
        template:"some template",
         link: function(scope, elem, attrs){
             console.log(attrs.chartData);
        }
      }
  }
  </code></pre>
  
  <p>here attrs.chartData displayes the data that was passed in root controller as $scope.salesData as json</p>
  
  <pre><code>app.directive('linearChart2', function($window){
     return{
        restrict:'EA',
        template:"some template",
         link: function(scope, elem, attrs){
             console.log(attrs.chartData);
        }
      }
  }
  </code></pre>
  
  <p>here chartData displays just the string ctrl.salesData2. How do I proceed thanks in advance.</p>