错误:在嵌套类中有不完整的类型|:

Question

我正在尝试声明类WRAPPED中的类型对象,WRAPPED并且该类WRAPPED包含在另一个名为的类中WRAPPER.我收到这些编译器错误.

nested_class_incomplete_type.cpp|56|instantiated from 'WRAPPER<NODE>'|
nested_class_incomplete_type.cpp|62|instantiated from here|
nested_class_incomplete_type.cpp|36|error: 'WRAPPER<T>::WRAPPED::WRAP' has incomplete type|
nested_class_incomplete_type.cpp|33|error: declaration of 'class WRAPPER<NODE>::WRAPPED'|

我也试过这样做WRAPPER::WRAPPED WRAP;但产生了同样的错误.如果WRAPPED类存在于类之外,这通常不会成为问题,但由于某种原因,它不允许我声明这样一个简单的对象.随意启发C++编译器语义和神Stroustrup的神奇世界.继承人的代码.

#include <iostream>

using namespace std;

class NODE
{
        int data;

    public:

        NODE(){}
        ~NODE(){}
        NODE(int data)
        {
            this->data = data;
        }
        void print()
        {
            std::cout<<"data: "<<this->data<<std::endl;
        }
};
template <class T>
class WRAPPER
{
    public:

        static T GLOBAL_WRAPPER_TYPE;

    WRAPPER(){}
    ~WRAPPER(){}

        class WRAPPED
        {
            public:

            WRAPPER::WRAPPED WRAP;

            WRAPPED(){}
            ~WRAPPED(){}
            void set(T GLOBAL_WRAPPER_TYPE)
            {
                WRAPPER::GLOBAL_WRAPPER_TYPE = GLOBAL_WRAPPER_TYPE;
            }
            T& get()
            {
                return GLOBAL_WRAPPER_TYPE;
            }
            WRAPPED& operator=(const WRAPPED &INSIDE)
            {
                GLOBAL_WRAPPER_TYPE = INSIDE.GLOBAL_WRAPPER_TYPE;

                return *this;
            }
        };

        WRAPPED INSIDE;
};
template <class T>
T WRAPPER<T>::GLOBAL_WRAPPER_TYPE;
int main()
{
    WRAPPER<NODE> WRAPPING;
    WRAPPING.INSIDE.set(NODE(99));
    NODE temp = WRAPPING.INSIDE.get();
    temp.print();

    return 0;
}

Answer 1

基本上你要做的是:

class A
{
    A a;
};

int main()
{
    A a;
    return 0;
}

(你可以看到,这将产生同样的错误在这里)

这是无限递归,您使用自己定义类型.改为使用指针,如下所示:

class A
{
    A* a;
};

int main()
{
    A a;

    return 0;
}

正如你在这里看到的那样编译.