class Window { // base class
public:
virtual void onResize() { ... } // base onResize impl
...
};
class SpecialWindow: public Window { // derived class
public:
virtual void onResize() { // derived onResize impl;
static_cast<Window>(*this).onResize(); // cast *this to Window,
// then call its onResize;
// this doesn't work!
... // do SpecialWindow-
} // specific stuff
...
};
Effective C++: What you might not expect is that it does not invoke that function on the current object! Instead, the cast creates a new, temporary copy of the base class part of *this, then invokes onResize on the copy!
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Contrast:
static_cast<Window>(*this)with:
static_cast<Window&>(*this)One calls the copy constructor, the other does not.
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Because you are casting actual object not a pointer or reference. It's just the same with casting double to int creates new int - not reusing the part of double.
double类型转换为int型会创建一个新的int型变量？
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上面的句子static_cast<Window>(*this).onResize();千万别改成下面这样,那样会更悲惨!
}