C ++ Lambda-捕获成员变量 [英] C++ lambda - capture member variable

问题描述

我有一个具有指向内核函数的函数指针的类，该类可以从外部更改。

I have a class that has function pointer to kernel function, that can change from outside.

class Bar 
{
   public:
     int i;
}

class Foo 
{
   public:
     std::function<double()> kernel;
     Bar bar;         
};

int main()
{

  Foo f;
  f.kernel = []() -> double { return i * i; }; //this is not working obviously

}

如何实现行为例如呈现。读取lambda中的类变量。我可以通过在内部传递 f 并编写 f.bar.i 来绕过它，但这不是很好的解决方案。

How can I achieve behaviour that is "presented", eg. read class variables inside lambda. I can bypass it by passing f inside and write f.bar.i, but that is not very nice solution.

推荐答案

在C ++ 14中，您可以将其编写为：

In C++14 you can write it as,

f.kernel = [&i = f.bar.i]() -> double { return i * i; };

如果您没有C ++ 14，也可以创建另一个变量，

If you don't have C++14, you can alternatively create another variable,

int &i = f.bar.i;
f.kernel = [&i]() -> double { return i*i; };

尽管通过 f 并没有错编写 f.bar.i 。

Though there's nothing wrong with passing f and writing f.bar.i.

这篇关于C ++ Lambda-捕获成员变量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！