将C ++成员函数指针传递给STL算法 [英] Passing a C++ Member Function Pointer to an STL Algorithm

问题描述

我的成员函数如下:

class XYZ{
public:
    float function(float x);
private:
    float m_DensityMin;
    float m_DensityMax;
};

现在，我正在尝试转换 std :: vector< float>foo 使用 std :: transform STL算法，方法是传递成员函数 function ，并将结果值存储在向量 bar 中

Now, I'm trying to transform a std::vector<float> foo using the std::transform STL algorithm by passing the member function function, and storing the resulting values in a vector bar.

如果我将该函数用作全局函数，并且应该使用随机数据来表示该类的成员变量，那么它将正常工作.

If I use the function as a global function, with random data that should denote the member variables of the class, it works fine.

但是，由于该函数需要使用类的成员变量 m_DensityMin 和 m_DensityMax ，因此我需要将其用作成员函数.这是我尝试过的:

However, as the function requires the use of member variables m_DensityMin and m_DensityMax of the class, I need to use it as a member function. This is what I've tried:

std::transform(foo.begin(), foo.end(), bar.begin(), &XYZ::function);

但是我最终遇到了VS2010中的错误:

but I end up with the error in VS2010:

error C2065: term does not evaluate to a function taking 1 arguments

据我所知，我只传递了一个参数.有指针吗?这是一个类似的问题，我已经尝试过使用std::mem_fun，因为std :: mem_fn对我不可用，但无济于事.

As far as I can tell I'm passing only 1 argument. Any pointers? Here's a similar question, I've tried with std::mem_fun, as std::mem_fn is not available to me, but to no avail.

推荐答案

<代码> std :: mem_fun 本身仅为成员函数提供包装器，因此将在传递给其 operator()的第一个参数的上下文中调用该包装器.话虽如此，您需要绑定 的正确实例XYZ ，然后再将函数对象传递到 std :: transform 算法:

std::mem_fun itself only povides a wrapper for a member function, so that one will be invoked in the context of the first argument passed to its operator(). Having said that, you need to bind the proper instance of XYZ prior to passing the function object to the std::transform algorithm:

XYZ xyz;

std::transform(foo.begin(), foo.end(),
               std::back_inserter(bar),
               std::bind1st(std::mem_fun(&XYZ::function), &xyz));
//                  ~~~~~~^      ~~~~~~^                  ~~~^

演示

这篇关于将C ++成员函数指针传递给STL算法的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！