C ++从const对象返回非const引用(C++ returning non const reference out of const object)

C ++从const对象返回非const引用(C++ returning non const reference out of const object)

我有结构，其中包含参考

template <class T> struct RefContainer { RefContainer(T& t) : _r(t) {} T& getRef() { return _r; } private: T& _r; };

现在，另一个不可变的对象在其自身内部使用此结构，并在其中包含此对象：

RefContainer<char> _c;

当我使用那个不可变对象用点转换自己时，我得到一个const引用。 因为我在不可变对象编译器中调用了RefContainer对象的getRef，所以我违反了const的正确性。

RefContainer本身必须保持非const左值引用，但我喜欢链接不可变对象的调用以创建新的类似：

ImmubableObject obj; auto newObj = obj.copyWithSomeAttributes().modifyWithThisString("str"); // I'm on C++11 btw, so I can use everything C++11 has to offer

我如何以“正确”的方式解决这个问题（可能避免丑陋的const演员）？

I have structure that contains reference in it

template <class T> struct RefContainer { RefContainer(T& t) : _r(t) {} T& getRef() { return _r; } private: T& _r; };

Now, another object, which is immutable uses this structure inside itself and has this object in it like so:

RefContainer<char> _c;

When I use that immutable object to transform itself with a dot I get a const reference. Since I call getRef of RefContainer object inside the immutable objects compiler says I violate const correctness.

The RefContainer itself has to hold non-const lvalue reference but I'd love to chain calls on immutable object to create new ones like so:

ImmubableObject obj; auto newObj = obj.copyWithSomeAttributes().modifyWithThisString("str"); // I'm on C++11 btw, so I can use everything C++11 has to offer

How do I work this out the "right" way (possibly avoiding ugly const casts) ?

最满意答案

你应该尝试这样的事情：

template <class T> struct RefContainer { RefContainer(T& t) : _r(t) {} T& getRef() const { // ^^^^^ return _r; } private: T& _r; };

这样，无论RefContainer实例是否为const对象， T& reference都可以用作非const。

You should try something like this:

template <class T> struct RefContainer { RefContainer(T& t) : _r(t) {} T& getRef() const { // ^^^^^ return _r; } private: T& _r; };

This way, the T& reference can be used as non const, regardless the RefContainer instance is a const object or not.