将 bind1st 用于通过引用获取参数的方法

2021-12-22 00:00:00 visual-c++ c++

我有一个这样的结构:

struct A {
    void i(int i) {}
    void s(string const &s) {}
};

现在当我尝试这个时:

bind1st(mem_fun(&A::i), &a)(0);
bind1st(mem_fun(&A::s), &a)("");

第一行编译正常，但第二行报错:

The first line compiles OK, but the second generates an error:

c:program files (x86)microsoft visual studio 10.0vcincludexfunctional(299): error C2535: 'void std::binder1st<_Fn2>::operator ()(const std::basic_string<_Elem,_Traits,_Ax> &) const' : member function already defined or declared
          with
          [
              _Fn2=std::mem_fun1_t<void,A,const std::string &>,
              _Elem=char,
              _Traits=std::char_traits<char>,
              _Ax=std::allocator<char>
          ]
          c:program files (x86)microsoft visual studio 10.0vcincludexfunctional(293) : see declaration of 'std::binder1st<_Fn2>::operator ()'
          with
          [
              _Fn2=std::mem_fun1_t<void,A,const std::string &>
          ]
          c:worksourcesexception	estexceptionmain.cpp(33) : see reference to class template instantiation 'std::binder1st<_Fn2>' being compiled
          with
          [
              _Fn2=std::mem_fun1_t<void,A,const std::string &>
          ]

可能是什么问题?我该如何解决?

What could be the problem? How could I fix it?

似乎任何引用参数都有问题.因此，如果我将 i 方法更改为 void i(int &i) {}，我会收到类似的错误.

It seems that any reference argument is a problem. So if I change the i method to void i(int &i) {} I get a similar error.

推荐答案

std::bind1st 和 std::bind2nd 不接受接受引用参数的函子，因为它们本身形成对这些参数的引用.你可以

std::bind1st and std::bind2nd don't accept functors which take reference arguments, because they themselves form references to these arguments. You can

  1. 为函数输入使用指针而不是引用
  2. 使用 boost::bind
  3. 接受复制字符串的性能成本

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