title: Child component property doesn't change
body: <p>this is probably a simple error but i can't figure it out by myself.</p>
  
  <p>Let's say we have a parent component with a child component inside. This child component has the next property:</p>
  
  <pre><code>private n : Number = 0;
  </code></pre>
  
  <p>and a method:</p>
  
  <pre><code>plusOne(){
      this.n += 1;
  }
  </code></pre>
  
  <p>so, every time we call the "plusOne" method the "n" property increase it value by 1.
  If i call this method from inside the child component everything works just fine.
  The problem is that when a call the method from the parent component (using ViewChild), the property doesn't changes the value. Actually, using console.log i've checked that the method is successfully called and the property changes value during the life cycle of the method.</p>
  
  <p>In later troubleshooting i changed the property to</p>
  
  <pre><code>public n : Number = 0;
  </code></pre>
  
  <p>Then tried to directly access to it from the parent component</p>
  
  <pre><code>this.child.n = 1;
  </code></pre>
  
  <p>But the property still doesn't change.</p>