title: How to call $get from Vue.extend?
body: <p>Examples do not show how to call such function from Vue.extend. Now I am getting error:
  <code>ReferenceError: $get is not defined</code></p>
  
  <pre><code>var guestContent = Vue.extend({
        template: `
  
          &lt;p&gt;Guest content&lt;/p&gt;
        &lt;div v-for="question in questions"&gt;
         &lt;template v-if="question.isEnabled"&gt;
            &lt;h3 v-if="question.isEnabled"&gt;{{question.question}}&lt;/h3&gt;
  
            &lt;!-- First Level --&gt;
              &lt;div v-for="firstLevelAnswer in question.answers"&gt;                
                &lt;label v-if="!question.isRadioButton"&gt;&lt;span class="firstLevelAnswer"&gt;&lt;input type="checkbox" class="big-checkbox" v-on:onclick="setIsSelectedTrue()"/&gt;{{firstLevelAnswer.answer}}&lt;/span&gt;&lt;/label&gt;
                &lt;label v-if="question.isRadioButton"&gt;&lt;span class="firstLevelAnswer"&gt;&lt;input type="radio" class="big-checkbox" name="myvalue"/&gt;{{firstLevelAnswer.answer}}&lt;/span&gt;&lt;/label&gt;
                &lt;span v-if="firstLevelAnswer.isTextInput"&gt;&lt;input type="text"/&gt;&lt;/span&gt;
                     |  firstLevelAnswer.isSelected: {{firstLevelAnswer.isSelected}}  
  
              &lt;/div&gt;
           &lt;/template&gt;
        &lt;/div&gt;  
  
      &lt;/li&gt;
  
            `,
          data: function ()  {
            return {
               questions: []
            }
  
            },
            ready() 
            { 
              this.getQuestionsContent(),
              this.foo()
            },
            methods: 
            {
  
               getQuestionsContent()
               {
                  this.$http.get('http://127.0.0.1:8080/js/questions.json').then(function(response)
                  {
                    this.questions = response.data;
  
                  }); 
  
                },
                foo()
                {
                  console.log($get('questions.question')); //HERE IS PROBLEM
                }
  
            }
  
          }
          );
  </code></pre>
  
  <p>Also can I check of value <code>firstLevelAnswer.isSelected</code> from foo? How can I reach it? It's generated in <code>for</code> loop and do not like that it can exists here...</p>