QVariant 存放指针

QVariant v = QVariant::fromValue((void *) yourPointerHere);
yourPointer = (YourClass *) v.value<void *>();

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You can store many types of data into QVariant, like int, string, etc. Also you can store pointers, but only pointers to void (void ). But what happens when you want to set a property of a object to a instance of class, with setProperty, and after that, you want to retrieve that property? QVariant accepts void , so you can do something like the following, to store it into QVariant:

QVariant v = QVariat::FromValue((void *) yourPointerHere);

and then something like this, in order to retrieve it back from QVariant://你也可以恢复到指针

yourPointer = (YourClass *) v.value<void *>();

Having this done each time you have to get the property or set the property is a bit tendentious. We can make this more friendly, using templates:

template <class T> class VPtr
{
public:
    static T* asPtr(QVariant v)
    {
    return  (T *) v.value<void *>();
    }
    static QVariant asQVariant(T* ptr)
    {
    return QVariant::FromValue((void *) ptr);
    }
};

So how do you use this? Assuming you have a class MyClass, and you want to store a pointer to this class as a property of a QWidget, or any QObject, or you want to convert it to QVariant, you can do the following:

MyClass *p;
QVariant v = VPtr<MyClass>::asQVariant(p);
MyClass *p1 = VPtr<MyClass>::asPtr(v);

I think this is more developer friendly than having to write each time those conversion code sequences.

转载：http://ju.outofmemory.cn/entry/179497