title: Qt doesn't see include class
body: <p>I have strange problem with including class. I have the class:
  main.cpp:</p>
  
  <pre><code>#include "startwidget.h"
  #include &lt;QApplication&gt;
  #include &lt;QtPlugin&gt;
  
  int main(int argc, char *argv[])
  {
      QApplication a(argc, argv);
  
      StartWidget w;
      w.show();
  
      return a.exec();
  }
  </code></pre>
  
  <p>startwidget.h:</p>
  
  <pre><code>#ifndef STARTWIDGET_H
  #define STARTWIDGET_H
  
  #include &lt;QWidget&gt;
  #include "phonewidget.h"
  #include "servicearealogin.h"
  
  namespace Ui {
  class StartWidget;
  }
  
  class StartWidget : public QWidget
  {
      Q_OBJECT
  
  public:
      explicit StartWidget(QWidget *parent = 0);
      ~StartWidget();
  
  private:
      Ui::StartWidget *ui;
  
      PhoneWidget *phoneWidget;
      ServiceAreaLogin *serviceAreaLogin;
  };
  
  #endif // STARTWIDGET_H
  </code></pre>
  
  <p>servicearealogin.h:</p>
  
  <pre><code>#ifndef SERVICEAREALOGIN_H
  #define SERVICEAREALOGIN_H
  
  #include &lt;QWidget&gt;
  #include &lt;QTimer&gt;
  #include "startwidget.h"
  
  namespace Ui {
  class ServiceAreaLogin;
  }
  
  class ServiceAreaLogin : public QWidget
  {
      Q_OBJECT
  
  public:
      explicit ServiceAreaLogin(QWidget *parent = 0);
      ~ServiceAreaLogin();
  
  private:
      Ui::ServiceAreaLogin *ui;
      StartWidget *startWidget;
  
      void startWidgetInit();
  
  #endif // SERVICEAREALOGIN_H
  </code></pre>
  
  <p>The problem is that when I want to compile my program I get a error:</p>
  
  <p>/main.cpp:1: In file included from ../Fluidwash/main.cpp:1:</p>
  
  <p>/startwidget.h:6: In file included from startwidget.h:6:</p>
  
  <p>servicearealogin.h:22: błąd: unknown type name 'StartWidget'
      StartWidget *startWidget;
      ^</p>
  
  <p>I really don't understand why it can't find the StartWidget class if I included this in headers.</p>
  
  <p>Or maybe my include politic is bad?</p>
  
  <p>In my StartWidget QWidget I do serviceAreaLogin->show(), now I need do the same with startWidget to back to previous widget.</p>
  
  <p>I read it <a href="https://stackoverflow.com/questions/625799/resolve-header-include-circular-dependencies">Resolve header include circular dependencies</a> and for me I included .h of class that i created pointer. So why doesn't it see the class?</p>