Qt多重继承和信号 [英] Qt multiple inheritance and signals

问题描述

我有一个问题QT关于多个继承，因为QObject。我知道很多其他人有相同的问题，但我不知道我该如何解决它。

I'm having a problem with QT regarding multiple enheritance because of QObject. I know that a lot of others have the same problems but I don't know how I should fix it.

class NavigatableItem : public QObject
{
    Q_OBJECT

    signals:
        void deselected();
        void selected();
        void activated();
};

class Button : public NavigatableItem, public QToolButton
{
    Q_OBJECT

    ...
}

class MainMenuOption : public Button
{
    Q_OBJECT

    ...
}

当我这样做

MainMenuOption* messages = new MainMenuOption();
connect(messages, SIGNAL(selected()), SLOT(onMenuOptionSelected()))

我会得到错误：

QObject'是'MainMenuOption'的不明确的基础

QObject' is an ambiguous base of 'MainMenuOption'

为什么我让NavigatableItem从QObject继承的原因是因为信号。有办法吗？

The reason why I let NavigatableItem enherit from QObject because of the signals. Is there a way to do this?

编辑：

每个继承声明，仍然给我相同的错误：

Adding virtual to each inheritence declaration, still gives me the same error:

class NavigatableItem : public virtual QObject

class Button : public virtual NavigatableItem, public virtual QToolButton

class MainMenuOption : public virtual Button

即使在清除所有，运行qmake和构建所有之后。

Even after a 'clean all', 'run qmake' and 'build all'.

推荐答案

代码，但我过去做的是使其中一个（你的 NavigatableItem 在这种情况下）一个纯虚拟类，即接口。而不是使用信号宏，使它们是纯虚拟保护函数。然后从你的QObject派生类和接口乘法继承，并实现方法。

It requires a bit more code, but what I have done in the past is make one of them (your NavigatableItem in this case) a pure virtual class, i.e. interface. Instead of using the "signals" macro, make them pure virtual protected functions. Then multiply-inherit from your QObject-derived class as well as the interface, and implement the methods.

我知道这是有点争议，但避免多重实现继承成本确实解决了大量的问题和混乱。 Google C ++风格指南推荐了这一点，我认为这是个好建议。 p>

I know it is somewhat controversial, but avoiding multiple implementation inheritance at all costs does solve a host of problems and confusion. The Google C++ Style Guidelines recommend this, and I think it is good advice.

class NavigatableItemInterface
{
    // Don't forget the virtual destructor!
    protected:
        virtual void deselected() = 0;
        virtual void selected() = 0;
        virtual void activated() = 0;
};

class Button : public NavigatableItemInterface, public QToolButton
{
    Q_OBJECT
    ...
    signals:
        virtual void deselected();
        ...
}

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