如何实现从模板化类派生的类

问：

我有 2 个项目的解决方案。在第一个构建为库的项目中，我有模板化类

啊

#pragma once

#include <memory>

template<class MessageType, class HandlerType>
class A
{
    std::unique_ptr<MessageType> msg;
    std::unique_ptr<HandlerType> handler;
public:
    A() : msg(std::make_unique<MessageType>()), handler(std::make_unique<HandlerType>()) {}
    virtual ~A() {}
};

然后是派生类

B.H.（英语：B.H）

#include "a.h"
#include <string>

struct MyMessage
{};
struct MyHandler
{};
class B : A<MyMessage, MyHandler>
{
    std::string name;
public:
    B(const std::string& str);
    virtual ~B();
};

并实施它

b.cpp

#include "b.h"

B::B(const std::string& str)
{
}

B::~B()
{}

此代码生成为静态库 （.lib）。但是当我尝试在主项目中使用 B 类的实例时：

进程.cpp

#include <iostream>
#include "b.h"

int main()
{
    std::cout << "Hello World!\n";
    B opa("yes");
}

编译器无法链接它

Rebuild started...
1>------ Rebuild All started: Project: ConsoleApplication3, Configuration: Debug Win32 ------
1>b.cpp
1>ConsoleApplication3.cpp
1>Generating Code...
1>ConsoleApplication3.vcxproj -> C:\Users\user\source\repos\tmpClass\Debug\ConsoleApplication3.lib
2>------ Rebuild All started: Project: tmpClass, Configuration: Debug Win32 ------
2>process.cpp
2>process.obj : error LNK2019: unresolved external symbol "public: __thiscall B::B(class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > const &)" (??0B@@QAE@ABV?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@@Z) referenced in function _main
2>process.obj : error LNK2019: unresolved external symbol "public: virtual __thiscall B::~B(void)" (??1B@@UAE@XZ) referenced in function _main
2>C:\Users\user\source\repos\tmpClass\Debug\tmpClass.exe : fatal error LNK1120: 2 unresolved externals
2>Done building project "tmpClass.vcxproj" -- FAILED.
========== Rebuild All: 1 succeeded, 1 failed, 0 skipped ==========