二进制'' ：未找到针对地图的操作符< std :: string，shared_ptr< Foo>> [英] binary '<' : no operator found for map<std::string, shared_ptr<Foo>>

问题描述

如何解决以下编译器错误：

  xstddef（180）：error C2678：binary'<'：没有操作符发现，它接受类型为const std :: string'（或没有可接受的转换）的左手操作数
 tuple（572）：可以是'bool std :: operator<（const std： ：const std :: string，const std :: string）'
（const std :: string，const std :: string） xstddef（179）：编译类模板成员函数'bool std :: less< _Ty> :: operator（）（const _Ty&，const _Ty&）const'
 with 
 [
 _Ty = std :: string 
] 
 map（177）：参见函数模板实例化的参考'bool std :: less< _Ty> :: operator（）（const _Ty&，const _Ty &）const'被编译
 with 
 [
 _Ty = std :: string 
] 
 type_traits（743）：参见类模板实例化'std： ：less <_Ty>'正在编译
 with 
 [
 _Ty = std :: string 
] 
 xtree（1028）：参见类模板实例化:: is_empty< _Ty>'编译
 with 
 [
 _Ty = std :: less< std :: string> 
] 
 map（67）：参见类模板实例化'std :: _ Tree< _Traits>'被编译
 with 
 [
 _Traits = std :: _Tmap_traits< std :: string，IDispatcherPtr，std :: less< std :: string>，std :: allocator< std :: pair< const std :: string，IDispatcherPtr>，false> 
] 
 main.cpp（506）：参见类模板实例化的参考'std :: map <_Kty，_Ty>'正在编译
 with 
 [
 _Kty = std :: string，
 _Ty = IDispatcherPtr 
] 
  

代码：

  class IDispatcher 
 {
 virtual void operator（） 
}; 
 
 class AlarmDispatcher：public IDispatcher 
 {
 virtual void operator（）
 {
} 
}; 
 
 typedef boost :: shared_ptr< IDispatcher> IDispatcherPtr; 
 
 int main（）
 {
 std :: map< std :: string，IDispatcherPtr>调度员
 dispatchers [alarm] = boost :: make_shared< AlarmDispatcher>（）; 
  

解决方案

第一个问题： / p>

您应该明确包含所有必需的标题，而不是依赖于通过包含其他标题间接包含的：

  #include< string> //< == INTICTICULAR THIS ONE 
 #include< map> 
 #include< boost / shared_ptr.hpp> 
 #include< boost / make_shared.hpp> 
  

从评论判断，你似乎包括< string.h> ; 头部（这是一个标准C库头部），而不是< string> 头部，其中定义了 std :: string 类。

第二个问题：

您忘记建立类之间的继承关系：

  class AlarmDispatcher：public IDispatcher 
 // ^^^^^^^^ 
 {
 virtual void operator（）
 {
} 
}; 
  

How can I resolve the following compiler error:

xstddef(180): error C2678: binary '<' : no operator found which takes a left-hand operand of type 'const std::string' (or there is no acceptable conversion)
          tuple(572): could be 'bool std::operator <(const std::tuple<> &,const std::tuple<> &)'
          while trying to match the argument list '(const std::string, const std::string)'
          xstddef(179) : while compiling class template member function 'bool std::less<_Ty>::operator ()(const _Ty &,const _Ty &) const'
          with
          [
              _Ty=std::string
          ]
          map(177) : see reference to function template instantiation 'bool std::less<_Ty>::operator ()(const _Ty &,const _Ty &) const' being compiled
          with
          [
              _Ty=std::string
          ]
          type_traits(743) : see reference to class template instantiation 'std::less<_Ty>' being compiled
          with
          [
              _Ty=std::string
          ]
          xtree(1028) : see reference to class template instantiation 'std::is_empty<_Ty>' being compiled
          with
          [
              _Ty=std::less<std::string>
          ]
          map(67) : see reference to class template instantiation 'std::_Tree<_Traits>' being compiled
          with
          [
              _Traits=std::_Tmap_traits<std::string,IDispatcherPtr,std::less<std::string>,std::allocator<std::pair<const std::string,IDispatcherPtr>>,false>
          ]
          main.cpp(506) : see reference to class template instantiation 'std::map<_Kty,_Ty>' being compiled
          with
          [
              _Kty=std::string,
              _Ty=IDispatcherPtr
          ]

for the following code:

class IDispatcher
{
    virtual void operator()() = 0;
};

class AlarmDispatcher: public IDispatcher
{
    virtual void operator()()
    {
    }
};

typedef boost::shared_ptr<IDispatcher> IDispatcherPtr;

int main()
{
    std::map<std::string, IDispatcherPtr> dispatchers;
    dispatchers["alarm"] = boost::make_shared<AlarmDispatcher>();

解决方案

First problem:

You should include explicitly all the necessary headers, and not rely on them being indirectly included through the inclusion of other headers:

#include <string> // <== IN PARTICULAR THIS ONE
#include <map>
#include <boost/shared_ptr.hpp>
#include <boost/make_shared.hpp>

Judging from the comments, it seems you included the <string.h> header (which is a Standard C library header) rather than the <string> header, which is where the std::string class is defined.

Second problem:

You forgot to establish the inheritance relationship between your classes:

class AlarmDispatcher : public IDispatcher
//                    ^^^^^^^^
{
    virtual void operator()()
    {
    }
};

这篇关于二进制'' ：未找到针对地图的操作符< std :: string，shared_ptr< Foo>>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！