我目前正在处理用VC ++编写的dependency injection example。我当前的设置基于writer（我的基类），一些测试类（我只是上传其中一个 - ＆gt; writer2）和我的圣杯，即通用类（{ {1}}），它应该完成整个依赖注入魔术。
但是每次我面对一些cpp代码时，链接器都不会在我的卡片中播放并跳过一些...很好......看...错误消息：
genericWriter PlusPlus_Example.obj : error LNK2001: unresolved external symbol "public: virtual void __thiscall genericWriter<class writer2>::print_whatever(class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> >)const " (?print_whatever@?$genericWriter@Vwriter2@@@@UBEXV?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@@Z)
writer.h // writer.h
#ifndef WRITER_H
#define WRITER_H
#include <string>
#include <boost/serialization/assume_abstract.hpp>
#include <boost/serialization/export.hpp>
#include <boost/serialization/nvp.hpp>
class writer
{
public:
writer::writer(void){}
virtual ~writer() {};
virtual void print_whatever(const std::string s) const = 0;
private:
friend class boost::serialization::access;
template<class Archive>
void serialize(Archive & ar, const unsigned int version) { }
};
BOOST_SERIALIZATION_ASSUME_ABSTRACT(writer)
#endif
writer2.h // writer.h
#ifndef WRITER2_H
#define WRITER2_H
#include "writer.h"
#include <boost/serialization/export.hpp>
class writer2 : public writer
{
public:
inline writer2(){}
void print_whatever(const std::string s) const override;
private:
friend class boost::serialization::access;
template<class Archive>
void serialize(Archive & ar, unsigned int file_version)
{
ar.template register_type<writer2>();
ar & BOOST_SERIALIZATION_BASE_OBJECT_NVP(writer);
}
};
#endif
writer2.cpp //writer2.cpp
#include "stdafx.h"
#include "writer2.h"
#include <iostream>
void writer2::print_whatever(const std::string s) const
{
std::cout << "-=" + s + "=-";
}
BOOST_CLASS_EXPORT_GUID(writer2, "writer2")
genericWriter.h // genericWriter.h
#ifndef GENERICWRITER_H
#define GENERICWRITER_H
#include "writer.h"
#include <boost/archive/text_oarchive.hpp>
#include <boost/archive/text_iarchive.hpp>
#include <boost/serialization/export.hpp>
#include <boost/serialization/shared_ptr.hpp>
template <typename T>
class genericWriter : public writer
{
public:
genericWriter(): _methodOfWriting(new T)
{
// Yes, the double parentheses are needed, otherwise the comma will be seen as macro argument separator
BOOST_STATIC_ASSERT((boost::is_base_of<writer, T>::value));
}
void print_whatever(const std::string s) const override;
private:
writer* _methodOfWriting;
friend class boost::serialization::access;
template<class Archive>
void serialize(Archive & ar, unsigned int file_version)
{
ar.template register_type<genericWriter<T>>();
ar & BOOST_SERIALIZATION_BASE_OBJECT_NVP(writer);
ar & BOOST_SERIALIZATION_NVP(_methodOfWriting);
}
};
genericWriter.cpp //genericWriter.cpp
#include "stdafx.h"
#include "genericWriter.h"
template<typename T>
void genericWriter<T>::print_whatever(const std::string s) const
{
(*_methodOfWriting).print_whatever(s);
}
// Exporting a template class not possible?
//BOOST_CLASS_EXPORT_GUID(genericWriter<T>, "genericWriter")
CPlusPlus_Example.cpp我的代码应该将// CPlusPlus_Example.cpp : Defines the entry point for the console application.
#include "stdafx.h"
#include "conio.h"
#include <string>
#include <boost/serialization/assume_abstract.hpp>
#include "genericWriter.h"
#include "writer2.h"
#include <fstream>
#include <boost/archive/xml_iarchive.hpp>
#include <boost/archive/xml_oarchive.hpp>
using namespace std;
int main()
{
// create and open a character archive for output
std::ofstream ofs("CPlusPlus_example.xml");
writer* test = new genericWriter<writer2>();
test->print_whatever("test");
// save data to archive
{
boost::archive::xml_oarchive oa(ofs);
// write class instance to archive
oa << BOOST_SERIALIZATION_NVP(test);
// archive and stream closed when destructors are called
}
{
// open the archive
std::ifstream ifs("CPlusPlus_example.xml");
assert(ifs.good());
boost::archive::xml_iarchive ia(ifs);
// restore the schedule from the archive
ia >> BOOST_SERIALIZATION_NVP(test);
}
test->print_whatever("test");
getch();
return 0;
}
保存到XML文件中或从XML文件中加载test（在此示例中称为＆＃34; CPlusPlus_example.xml ＆＃34;）应该看起来像以下内容：
<?xml version="1.0" encoding="UTF-8" standalone="yes" ?>
<!DOCTYPE boost_serialization>
<boost_serialization signature="serialization::archive" version="15">
<test type="genericWriter" class_id="0" tracking_level="1" version="0" object_id="_0">
<_methodOfWriting type="writer2" class_id="1" tracking_level="0" version="0">
<writer></writer>
</_methodOfWriting>
<writer></writer>
</test>
</boost_serialization>
因为我无法提升::导出我的genericWriter，它可能无法解决？但如果是这样的话 - 有没有办法使用＆＃34;通用模板类＆＃34;？
根据评论，我将代码更改为以下内容：
genericWriter.tpp
//genericWriter.tpp
#include "stdafx.h"
#include "genericWriter.h"
template<typename T>
void genericWriter<T>::print_whatever(const std::string s) const
{
(*_methodOfWriting).print_whatever(s);
}
genericWriter.h
// genericWriter.h
#ifndef GENERICWRITER_H
#define GENERICWRITER_H
#include "writer.h"
#include <boost/archive/text_oarchive.hpp>
#include <boost/archive/text_iarchive.hpp>
#include <boost/serialization/export.hpp>
#include <boost/serialization/shared_ptr.hpp>
#include "genericWriter.tpp"
template <typename T>
class genericWriter : public writer
{
public:
genericWriter(): _methodOfWriting(new T)
{
// Yes, the double parentheses are needed, otherwise the comma will be seen as macro argument separator
BOOST_STATIC_ASSERT((boost::is_base_of<writer, T>::value));
}
//void print_whatever(const std::string s) const override;
private:
writer* _methodOfWriting;
friend class boost::serialization::access;
template<class Archive>
void serialize(Archive & ar, unsigned int file_version)
{
ar.template register_type<genericWriter<T>>();
ar & BOOST_SERIALIZATION_BASE_OBJECT_NVP(writer);
ar & BOOST_SERIALIZATION_NVP(_methodOfWriting);
}
};
（并删除了genericWriter.cpp）
现在我得到更多错误\（^ - ^）/
1>e:\vsprograms\dependencyinjectionexamples\cplusplus_example\cplusplus_example\genericwriter.tpp(7): error C2988: unrecognizable template declaration/definition
1>e:\vsprograms\dependencyinjectionexamples\cplusplus_example\cplusplus_example\genericwriter.tpp(7): error C2143: syntax error: missing ';' before '<'
1>e:\vsprograms\dependencyinjectionexamples\cplusplus_example\cplusplus_example\genericwriter.tpp(7): error C2182: 'genericWriter': illegal use of type 'void'
1>e:\vsprograms\dependencyinjectionexamples\cplusplus_example\cplusplus_example\genericwriter.tpp(7): error C2059: syntax error: '<'
1>e:\vsprograms\dependencyinjectionexamples\cplusplus_example\cplusplus_example\genericwriter.tpp(8): error C2143: syntax error: missing ';' before '{'
1>e:\vsprograms\dependencyinjectionexamples\cplusplus_example\cplusplus_example\genericwriter.tpp(8): error C2447: '{': missing function header (old-style formal list?)
1>e:\vsprograms\dependencyinjectionexamples\cplusplus_example\cplusplus_example\writer2.h(12): error C2628: 'writer2' followed by 'void' is illegal (did you forget a ';'?)
1>e:\vsprograms\dependencyinjectionexamples\cplusplus_example\cplusplus_example\writer2.h(12): error C2270: 'print_whatever': modifiers not allowed on nonmember functions
1>e:\vsprograms\dependencyinjectionexamples\cplusplus_example\cplusplus_example\writer2.h(12): error C2259: 'writer2': cannot instantiate abstract class
1>e:\vsprograms\dependencyinjectionexamples\cplusplus_example\cplusplus_example\writer2.h(12): note: due to following members:
1>e:\vsprograms\dependencyinjectionexamples\cplusplus_example\cplusplus_example\writer2.h(12): note: 'void writer::print_whatever(const std::string) const': is abstract
1>e:\vsprograms\dependencyinjectionexamples\cplusplus_example\cplusplus_example\writer.h(17): note: see declaration of 'writer::print_whatever'
1>e:\vsprograms\dependencyinjectionexamples\cplusplus_example\cplusplus_example\writer2.h(15): error C2059: syntax error: 'private'
1>e:\vsprograms\dependencyinjectionexamples\cplusplus_example\cplusplus_example\writer2.h(16): error C2255: 'friend': not allowed outside of a class definition
1>e:\vsprograms\dependencyinjectionexamples\cplusplus_example\cplusplus_example\writer2.h(27): error C2059: syntax error: '}'
1>e:\vsprograms\dependencyinjectionexamples\cplusplus_example\cplusplus_example\writer2.h(27): error C2143: syntax error: missing ';' before '}'
1>e:\vsprograms\dependencyinjectionexamples\cplusplus_example\cplusplus_example\cplusplus_example.cpp(22): error C2061: syntax error: identifier 'genericWriter'
那可能是因为genericWriter的print_whatever函数的定义不再在genericWriter.h中了？