Question

所有，我正在玩弄了解r值，l值以及scott meyers所谓的“通用参考”。我在设置示例时遇到了一些问题，如下所示。有人可以提供一些指导吗？

#include <cstdio>

namespace who_needs_namespaces {

class SomeSillyClass {
    public:
    SomeSillyClass() {
        printf("Default constructed.\n");
    }
    SomeSillyClass(const SomeSillyClass& rhs) {
        printf("L-Value constructed.\n");
    }
    SomeSillyClass(SomeSillyClass&& rhs) {
        printf("R-Value Constructed.\n");   
    }

    void doStuff() const {
        printf("doing...\n");
    }
};

template<typename T>
class HolderByValue {
public:
    HolderByValue() = delete;   
    HolderByValue(T toHold) : m_mine(toHold) 
    { }; 

private:
    T m_mine;
};

template<typename T>
class HolderByRef {
public:
    HolderByRef() = delete;   
    HolderByRef(T&& toHold) : m_mine(toHold)
    { }; 

private:
    T m_mine;
};

}

using namespace who_needs_namespaces;

int main() {
    //Check our silly class.
    SomeSillyClass defaultCtr;
    defaultCtr.doStuff();
    SomeSillyClass copyCtr(defaultCtr);
    copyCtr.doStuff();
    SomeSillyClass moveCtr(SomeSillyClass);
    moveCtr.doStuff();

    //Check our HolderByValue
    //HolderByValue<SomeSillyClass> holder(defaultCtr);
    HolderByValue<SomeSillyClass &> holder(defaultCtr);

}

main.cpp: In function 'int main()':
main.cpp:59:13: error: request for member 'doStuff' in 'moveCtr', which is of non-class type 'who_needs_namespaces::SomeSillyClass(who_needs_namespaces::SomeSillyClass)'

Answer 1

我认为你已经成为Scott Meyers所说的C ++最烦恼的解决方案的受害者。 https://en.wikipedia.org/wiki/Most_vexing_parse

移动构造函数抱怨“非类型”

1 个答案: