C++“致命错误LNK1120"未解析的静态类成员

C++ quot;fatal error LNK1120quot; unresolved static class members(C++“致命错误LNK1120未解析的静态类成员)

问题描述

我收到以下错误消息(有人可以随意编辑不必要的位):

I get the following error message (someone feel free to edit the unnecessary bits):

1>FIXDecoder.obj:错误 LNK2001:未解析的外部符号私有:静态类 std::unordered_map,class std::allocator >,classstd::basic_string, 类std::allocator >,struct std::hash,classstd::allocator > >,struct std::equal_to,classstd::allocator > >,class std::allocator,classstd::allocator > const ，类 std::basic_string，类 std::allocator > > > >FD::FixValueMappingsDict"(?FixValueMappingsDict@FD@@0V?$unordered_map@V?$basic_string@DU?$char_traits@D@V?$allocator@D@V12@U?$hash@V?$basic_string@DU?$char_traits@D@V?$allocator@D@U?$equal_to@V?$basic_string@DU?$char_traits@D@V?$allocator@D@V?$allocator@U?$pair@$$CBV?$basic_string@DU?$char_traits@D@V?$allocator@D@V12@@@A)

1>FIXDecoder.obj : error LNK2001: unresolved external symbol "private: static class std::unordered_map,class std::allocator >,class std::basic_string,class std::allocator >,struct std::hash,class std::allocator > >,struct std::equal_to,class std::allocator > >,class std::allocator,class std::allocator > const ,class std::basic_string,class std::allocator > > > > FD::FixValueMappingsDict" (?FixValueMappingsDict@FD@@0V?$unordered_map@V?$basic_string@DU?$char_traits@D@V?$allocator@D@V12@U?$hash@V?$basic_string@DU?$char_traits@D@V?$allocator@D@U?$equal_to@V?$basic_string@DU?$char_traits@D@V?$allocator@D@V?$allocator@U?$pair@$$CBV?$basic_string@DU?$char_traits@D@V?$allocator@D@V12@@@A)

1>FD.obj : error LNK2001: 未解析的外部符号private: static类 std::unordered_map, 类 std::allocator >, 类std::basic_string, 类std::allocator >,struct std::hash,classstd::allocator > >,struct std::equal_to,classstd::allocator > >,class std::allocator,classstd::allocator > const ，类 std::basic_string，类 std::allocator > > > >FD::FIXFieldNoDict"(?FIXFieldNoDict@FD@@0V?$unordered_map@V?$basic_string@DU?$char_traits@D@V?$allocator@D@V12@U?$hash@V?$basic_string@DU?$char_traits@D@V?$allocator@D@U?$equal_to@V?$basic_string@DU?$char_traits@D@V?$allocator@D@V?$allocator@U?$pair@$$CBV?$basic_string@DU?$char_traits@D@V?$allocator@D@V12@@@A)

1>FD.obj : error LNK2001: unresolved external symbol "private: static class std::unordered_map,class std::allocator >,class std::basic_string,class std::allocator >,struct std::hash,class std::allocator > >,struct std::equal_to,class std::allocator > >,class std::allocator,class std::allocator > const ,class std::basic_string,class std::allocator > > > > FD::FIXFieldNoDict" (?FIXFieldNoDict@FD@@0V?$unordered_map@V?$basic_string@DU?$char_traits@D@V?$allocator@D@V12@U?$hash@V?$basic_string@DU?$char_traits@D@V?$allocator@D@U?$equal_to@V?$basic_string@DU?$char_traits@D@V?$allocator@D@V?$allocator@U?$pair@$$CBV?$basic_string@DU?$char_traits@D@V?$allocator@D@V12@@@A)

1>C:visual studio 2012ProjectsFDx64DebugFD.exe:致命错误LNK1120:2 个未解析的外部

1>C:visual studio 2012ProjectsFDx64DebugFD.exe : fatal error LNK1120: 2 unresolved externals

对于此代码:

//FH.h
#ifndef FD_H
#define FD_H

#include "FM.h"
#include <unordered_map>
#include <string>

class FD{
public:
    FD();
    FD(FM message);
    ~FD();
    FD(const FD& tocopy);
    FD& operator=(const FD& toassign);

private:
    static unordered_map<string,string> FIXFieldNoDict;
    static unordered_map<string,string> FixValueMappingsDict;
};

#endif

//FD.cpp
#include "FD.h"
#include "Mappings.h"
#include "Utils.h"
#include <vector>
#include <string>
#include <iostream>
#include <unordered_map>

using namespace std;

FD::FD(){
    FIXFieldNoDict = Mappings::createFIXFieldNoDict();
    FixValueMappingsDict = Mappings::getFIXValuesDict();
}

Mappings.h 只包含一些创建 unordered_map 的函数

Mappings.h just contains some functions which create an unordered_map

#ifndef MAPPINGS_H
#define MAPPINGS_H

#include <unordered_map>
#include <string>

using namespace std;

class Mappings{

public:
    Mappings();

    static unordered_map<string,string> createFIXFieldNoDict();

    static unordered_map<string,string> getFIXValuesDict();
.
.
};

推荐答案

您需要在 FD.cpp 文件中创建静态成员的实例:

You need to create instances of your static members in the FD.cpp file:

//FD.cpp
#include "FD.h"
#include "Mappings.h"
#include "Utils.h"
#include <vector>
#include <string>
#include <iostream>
#include <unordered_map>

using namespace std;

unordered_map<string,string> FD::FIXFieldNoDict = Mappings::createFIXFieldNoDict();
unordered_map<string,string> FD::FixValueMappingsDict = Mappings::getFIXValuesDict();


FD::FD(){
}

注意你不应该在 FD 构造函数中初始化它们，因为你可以在构造任何对象之前使用静态成员(并且你需要初始化它们一次而不是每次当某个对象被构造).

Note that you shouldn't initialize them in the FD constructor, as you can use static members before construction of any object (and you need to initialize them once and not every time when some object is constructed).

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