在VS 2017中，朋友通过具有私有析构函数的结构的unique_ptr向量进行迭代失败

Iterating through vector of unique_ptr of a struct with private destructor, by a friend, fails in VS 2017

本文关键字：结构 unique ptr 向量 失败 迭代 2017 VS 朋友 析构函数      更新时间：2023-10-16

这可能是一个答案很简单的问题，但我尝试了谷歌结果提供的所有解决方案，但无法在VS 2017中解决这个问题。我有一个带有私有析构函数的结构B。我有另一个结构A，它是结构B的朋友，并试图遍历结构B的唯一指针向量。但我一直收到这个错误：

严重性代码描述项目文件行禁止显示状态错误C2248"ProjectNamespace:：NwSpec:：~NwSpec"：无法访问类"ProjectNamespace：：NwSpec"TestProject c:\program files(x86(\microsoft visual studio\2017\community\vc\tools\msvc\14.14.26428\include\memory 2055 中声明的私有成员

任何指针都将不胜感激。谢谢

struct A
{
//functions
std::vector<std::unique_ptr<NwSpec>> List;
bool function()const;
};
struct NwSpec
{
char* Path;//Assume Path is initialized and set with a string.
private:
~NwSpec();
friend struct A;
};
bool A::function()const 
{
for (uint32_t i = 0 ; i < List.size(); i++)
{
OutputDebugStringA(List[i]->Path);// Error C2248
}
// I used iterator to the vector, but getting same error.
// I used for(const auto& k : List) but getting same access error.
// NwSpec is visible to A and within ProjectNamespace
}

您需要创建一个专门的类型来负责NwSpec对象的删除，并将其提供给std::unique_ptr:

struct NwSpec;
struct A {
private:
struct NwSpecDeleter {
//Note that we're only declaring the function, and not defining it
void operator()(NwSpec * ptr) const;
};
public:
typedef std::unique_ptr<NwSpec, NwSpecDeleter> ptr_type;
std::vector<ptr_type> List;
bool function()const;
};
struct NwSpec {
char* Path;//Assume Path is initialized and set with a string.
private:
~NwSpec();
friend struct A;
};
NwSpec::~NwSpec() {}
void A::NwSpecDeleter::operator()(NwSpec * ptr) const {
delete ptr;
}
int main() {
A a;
a.List.emplace_back(new NwSpec());
auto ptr = a.List.back().release();
//This will not compile, as intended
//delete ptr;
//Nor will this:
//ptr->~NwSpec();
//But this will compile, because the original unique_ptr is perfectly capable of deleting objects:
a.List.back().reset(ptr);
a.List.back().reset();//Object is successfully deleted
a.List.erase(a.List.begin(), a.List.end());
a.List.emplace_back(new NwSpec());
//This also compiles
a.List.erase(a.List.begin(), a.List.end());
return 0;
}

此代码可以在此处进行测试。

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