Qmenu addMenu回报派生类对象

Question

我这是从QMenu派生的类，但IA中号无法返回的派生类对象

myMenu * editMenu = new myMenu(); // myMenu is derived from QMenu 
myMenu *preferenceMenu = new myMenu(); 
preferenceMenu = editMenu->addMenu(tr("&Preferences")); // this shows error 

QMenu *preferenceMenu = new QMenu(); 
preferenceMenu = editMenu->addMenu(tr("&Preferences")); // this works fine 

Answer 1

QMenu::addMenu返回一个指向QMenu ...

QMenu *QMenu::addMenu(const QString &title); 

所以隐含低垂到myMenu *将在下面的失败...

myMenu *preferenceMenu = editMenu->addMenu(tr("&Preferences")); 

如果你想添加自己的自定义的子菜单类型，然后使用提供了功能QMenu::addMenu overload ...

auto *preferences_menu = new myMenu(tr("&Preferences"); 
editMenu->addMenu(preferences_menu);