title: Ionic 2 - ViewChild component is undefined
body: <p><strong>THE SITUATION</strong>:</p>
  
  <p>From the app component I need to call a method in another component.</p>
  
  <p>I read that <code>@ViewChild</code> is the way to do it.</p>
  
  <p>But is not working in my case. I am getting the following error:</p>
  
  <pre><code>Cannot read property ... of undefined
  </code></pre>
  
  <p><strong>THE CODE</strong>:</p>
  
  <p>This for example is a simple test method inside the <strong>HomePage component</strong>:</p>
  
  <pre><code>testChild()
  {
      alert('child working');
  }
  </code></pre>
  
  <p>In the <strong>app.component</strong> I declare HomePage as the child component: </p>
  
  <pre><code>@ViewChild(HomePage) homePage: HomePage;
  </code></pre>
  
  <p>and then call the method from the constructor:</p>
  
  <pre><code>this.homePage.testChild();
  </code></pre>
  
  <p>It should work right?</p>
  
  <p>Instead I am getting this error:</p>
  
  <p><a href="https://i.stack.imgur.com/EL78L.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/EL78L.png" alt="enter image description here"></a></p>
  
  <p>The problem is not that the view is not loaded yet.</p>
  
  <p>I have tried also to call the child from a click event and got the same error.</p>
  
  <p><strong>THE QUESTION</strong>:</p>
  
  <p>Why is the child component is undefined?</p>
  
  <p>Do you know what am I doing wrong?</p>
  
  <p>Thanks!</p>