C ++ Lambda捕获私有类成员 [英] C++ Lambda capture private class member
问题描述
这是我班的一部分:
//...
bool dump_dvars()
{
fstream& refvar{ output_file };
for_each(_array_start, _array_start + *_array_size,
[&refvar](const void* dvar) -> void
{
//work with output_file
});
return true;
}
private:
void** _array_start;
unsigned int* _array_size;
fstream output_file;
};
我想访问Lambda的私有成员变量output_file,该变量位于公共成员函数dump_dvars中。当我捕获this指针时,因为它是私有变量,所以我无法访问该变量,但是我也不想将其设置为公用!我已经读过这个问题(如何制作lambda类的朋友?),但我不想创建另一个函数。因此,我目前针对该问题的解决方法是创建对私有成员的引用,并将该变量通过引用捕获列表传递给我的Lambda。
I want to access the private member variable output_file of my Lambda, which is in the public member function dump_dvars. When I capture the this pointer I can not access the variable because it is private, I also don't want to make it public though! I already read this question (How to make the lambda a friend of a class?) but I don't want to create another function. So my current fix for the problem is creating a reference to the private member and pass that variable via reference capture list to my Lambda.
这是一个好的解决方案和好的样式还是有更好的解决方案?
Is that a good solution and good style or is there a better solution?
推荐答案
您应该在lambda中捕获 this。
You should capture 'this' in the lambda.
下面的代码可以与g ++,clang,VS2010和VS2013一起编译并正常工作。
The following code compiles and works just fine with g++, clang, VS2010 and VS2013.
#include <iostream>
class A
{
public:
A() : x(5){}
void f() const
{
([this]()
{
std::cout << x << std::endl;
})();
}
private:
int x;
};
int main()
{
A a;
a.f();
}
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