Mediator - 中介者模式

class Mediator {
public:
    virtual void showDialog() = 0;
    virtual void widgetChanged(Widget*) = 0;
protected:
     Mediator();
     virtual void createWidgets() = 0;
};

class Widget {
public:
    Widget(Mediator* mediator) { m_mediator = mediator; }
    virtual void changed(){ }
    Mediator* mediator() const { return m_mediator; }
private:
    Mediator* m_mediator; 
};

class LineEdit : public Widget {
public:
    LineEdit(Mediator*);
    virtual void changed();
    void setText(const string& text);
    string text() const;
private:
    string m_text;
};
void LineEdit::changed() 
{
    mediator()->widgetChanged(this);
}

class DialogMediator : public Mediator {
public:
    virtual void widgetChanged(Widget* widget);
    virtual void showDialog();
protected:
    virtual void createWidgets();
private:
    LineEdit* m_lineEdit;
    ListBox* m_listBox;
    Button* m_button;
};
void DialogMediator::createWidgets()
{
    m_lineEdit = new LineEdit();
    ...
}
void DialogMediator::widgetChanged(Widget* widget)
{
    if(widget == m_lineEdit)
    {
        m_listBox->setSelection(m_lineEdit->text());
        m_button->setEnable(true);
    }
    else if(m_listBox)
    {
        m_lineEdit->setText(m_listBox->getSeletion());
        m_button->setEnable(true);
    }
    else
    {
        m_lineEdit->setText("");
        m_listBox->setSelection(lastOne);
    }
}