title: "Undefined reference" error in Qt Creator
body: <p>I'm trying to import some working Visual C++ code into Qt Creator and I'm having some compilation error I can't explain. This is my code:</p>
  
  <pre><code>// TabSprite.h
  
  #include &lt;GraphicsItem.h&gt;
  
  namespace appetizer {
  
  class TabSprite : public GraphicsItem {
  
  public:
  
    TabSprite(GraphicsWindow* parentWindow);
  
  }
  </code></pre>
  
  <hr>
  
  <pre><code>// TabSprite.cpp
  
  #include &lt;TabSprite.h&gt;
  using namespace appetizer;
  
  TabSprite::TabSprite(GraphicsWindow* parentWindow): GraphicsItem(parentWindow) {
  
  }
  </code></pre>
  
  <p>And Qt Creator give me this error (at the constructor declaration in <code>TabSprite.cpp</code>):</p>
  
  <blockquote>
    <p>Undefined reference to 'appetizer::GraphicsItem::GraphicsItem(appetizer::GraphicsWindow*)</p>
  </blockquote>
  
  <p>However <code>GraphicsItem</code> is properly declared in <code>GraphicsItem.h</code> so I don't understand why the compilers doesn't find it. Can anybody see what could be wrong with this code?</p>