[英]What is the difference between private and protected members of C++ classes?
[英]How to share protected members between C++ template classes?
請考慮以下示例:
class _ref
{
public:
_ref() {}
_ref(const _ref& that) {}
virtual ~_ref() = 0;
};
_ref::~_ref() {}
template <typename T>
class ref : public _ref
{
protected:
ref(const _ref& that) {}
public:
ref() {}
ref(const ref<T>& that) {}
virtual ~ref() {}
template <typename U>
ref<U> tryCast()
{
bool valid;
//perform some check to make sure the conversion is valid
if (valid)
return ref<U>(*this); //ref<T> cannot access protected constructor declared in class ref<U>
else
return ref<U>();
}
};
我希望所有類型的'ref'對象能夠訪問彼此的受保護構造函數。 有沒有辦法實現這個目標?
template <typename T>
class ref : public _ref
{
template <typename U>
friend class ref;
//...
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