Design Pattern --- Mediator

class AList;
class AButton;
class AEdit;

class Director
{
    // data.
    AList *m_list;
    AButton *m_button;
    AEdit *m_edit;

public:
    // Interface.
    void Init(AList *l, AButton *b, AEdit *e) 
    {
        m_list = l, 
        m_button = b, 
        m_edit = e;
    }

    void foo_bazBar();
    void bar_baz();
};

class AList
{
    // data.
    Director *m_director;

public:
    AList(Director *d) : m_director(d) {}
public:
    // Interface
    void foo() 
    { 
        cout <<"AList::foo()." <<endl; 
        m_director->foo_bazBar();            // 通过 Director 通知其它的控件.
    }
};
class AButton
{
    // data.
    Director *m_director;

public:
    AButton(Director *d) : m_director(d) {}
public:
    // Interface
    void bar() 
    { 
        cout <<"AButton::bar()." <<endl; 
        m_director->bar_baz();            // 通过 Director 通知其它的控件.
    }
};
class AEdit
{
    // data.
    Director *m_director;

public:
    AEdit(Director *d) : m_director(d) {}
public:
    // Interface
    void baz() { cout <<"AEdit::baz()." <<endl; }
};

void Director::foo_bazBar()
{
    m_edit->baz();
    m_button->bar();
}
void Director::bar_baz()
{
    m_edit->baz();
}

int main()
{
    Director *d = new Director;
    AList *l = new AList(d);
    AButton *b = new AButton(d);
    AEdit *e = new AEdit(d);
    d->Init(l, b, e);

    l->foo();

    // TODO: Release memory.

    return 0;
}

此模式与 Observer 模式非常相似, 都是找一个转发中心 (此例中 Directory), 作为所有不相关控件 (如 AList 和 AButton) 的控制者. 这些不相关的控件, 向 Director 申请一些操作, Director 便会找到相应的对象并执行操作.