多個文件困難的模板

您好我無法掌握如何在文件中組織我的模板類。我看過C++ templates, undefined reference ，並試圖使用http://www.parashift.com/c++-faq-lite/templates.html#faq-35.12中給出的提示來分隔我的頭文件和實現文件。多個文件困難的模板

#include "Variables.h" 

    int main() { 
Pressure<float,double> first(7.9,"atm"); 
return 0; 
    }

變量是我的頂級課程，爲了簡潔，我刪除了一些函數。

/* 
* Variable_Parent.h 
* 
* Here an abstract base class from which variables can be derived is defined. 
* 
*/ 

#ifndef PARENT_VARIABLE_H_ 
#define PARENT_VARIABLE_H_ 

#include <string> 
#include <map> 

template <typename V,typename D> // To let different variables use different S.F. 
struct Variable{ 
    /* 
    * This structure is a abstract base class from which all dimensional variables 
    * are derived. Derived variables may be operated with and units will be largely 
    * automatically handled. 
    */ 

protected: 
    //Functions 
    Variable(V v, std::string u, D conversions [], std::map<std::string,short> units); 
    ~Variable(); 

    //Variables 
    V value; 
    std::string unit; 
    std::map<std::string, unsigned short> * valid_units; //contains all units for which conversions have been defined. 
    D * conversion; //An n by n array for calculating conversions 

public: 
    V get_value() const; 
    std::string get_unit() const; 
    void change_unit(std::string new_unit); 


     #endif /* PARENT_VARIABLE_H_ */

我的實現：

/* 
    * Header files 
    */ 
    #include "Variables_Parent.h" 
    #include <string> 
    #include <map> 
    #include <typeinfo> 

    template<typename V,typename D> 
    Variable<V,D>::Variable(V v, std::string u, D conversions [], std::map<std::string,short> units){ 
     value = v; 
     unit = u; 
     conversion = conversions; 
     valid_units = &units; 
    } 

    template <typename V,typename D> 
    V Variable<V,D>::get_value() const{ 
      return this.value; 
     } 

    template <typename V,typename D> 
    std::string Variable<V,D>::get_unit() const{ 
     return unit; 
    } 

template <typename V,typename D> 
void Variable<V,D>::change_unit(std::string new_unit){ 
    if (valid_units->find(new_unit) == valid_units->end()){//Check the unit is defined 
     std::string message("%s is not a valid unit. /n", new_unit); 
     warning(message); 
    } 
    else{ 
     int target = (*valid_units)[new_unit]; 
     int original = (*valid_units)[unit]; 
     int width = valid_units->size(); 
     value*=conversion[ (original*width) + target]; 
     unit=new_unit; 
    } 
}

現在我希望能夠創造這本不同類的專業情況，其中valid_units和轉換點，我知道我可以給這個作爲選項在構造函數中，但其中很多可能會創建我想要一個簡單的構造函數。所以：

/* 
* Variables.h 
* 
* Here all the variable classes are defined. 
* 
* Created on: Nov 16, 2011 
*  Author: 
*/ 

#ifndef VARIABLES_H_ 
#define VARIABLES_H_ 

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


/////////////////////////////////////////////////////////////////////////////////////////////////////// 
/* 
* Pressure 
*/ 
template <typename V,typename D> 
class Pressure : Variable<V,D> { 
public: 
    Pressure(V v,std::string u); 
    ~Pressure(); 
};

。在我註釋掉底部的執行文件中的兩個模板類聲明，我試圖使用由parashift常見問題的建議，這些行給我的控制檯錯誤：

Invoking: GCC C++ Compiler 
g++ -O0 -g3 -Wall -c -fmessage-length=0 -MMD -MP -MF"src/Variables.d" -MT"src/Variables.d" -o"src/Variables.o" "../src/Variables.cpp" 
../src/Variables.cpp: In constructor ‘Pressure<V, D>::Pressure(V, std::string) [with V = float, D = double, std::string = std::basic_string<char>]’: 
../src/Variables.cpp:27:16: instantiated from here 
../src/Variables.cpp:22:43: error: no matching function for call to ‘Variable<float, double>::Variable()’ 
../src/Variables_Parent.h:26:2: note: candidates are: Variable<V, D>::Variable(V, std::string, D*, std::map<std::basic_string<char>, short int>*) [with V = float, D = double, std::string = std::basic_string<char>] 
../src/Variables_Parent.h:17:16: note:     Variable<float, double>::Variable(const Variable<float, double>&) 
../src/Variables.cpp:23:2: error: no matching function for call to ‘Variable<float, double>::Variable(float&, std::string&, double [3], const std::map<std::basic_string<char>, short unsigned int>&)’ 
../src/Variables_Parent.h:26:2: note: candidates are: Variable<V, D>::Variable(V, std::string, D*, std::map<std::basic_string<char>, short int>*) [with V = float, D = double, std::string = std::basic_string<char>] 
../src/Variables_Parent.h:17:16: note:     Variable<float, double>::Variable(const Variable<float, double>&) 
make: *** [src/Variables.o] Error 1

/* 
* Variables.c++ 
* 
* Created on: Nov 18, 2011 
*  Author: 
*/ 

#include "Variables.h" 
#include <string> 
#include <boost/assign.hpp> 

/////////////////////////////////////////////////////////////////////////////////////////////////////// 
/* 
* Pressure 
*/ 
const static std::map<std::string, unsigned short> PRESSURE_UNITS = 
    boost::assign::map_list_of("kPa",0)("atm",1)("psi",2);// might want new 

static double PRESSURE_CONVERSION[3][3]= {{1,0.009869232667,0.145037738},{101.325,1,14.6959488},{6.89475729,0.0680459639,1}}; 

template <typename V,typename D> 
Pressure<V,D>::Pressure(V v, std::string u){ 
    Variable<V,D>(v,u,PRESSURE_CONVERSION[0],PRESSURE_UNITS); 
} 

/* 
template class Pressure<float, double>; 
template class Variable<float, double>; 
/*

當我不包括在主我得到試圖建立第一個錯誤的聲明。在這條線多個標記 - 未定義參考Pressure<float, double>::~Pressure()' - undefined reference to壓力::壓力（浮動，性病:: basic_string的，性病::分配器

)'

對不起我想確保我包括給所有相關信息的長度在這一點上，我沒有線索在此先感謝我希望我不會將我的實現移動到我的標題

來源

2011-11-22 wookie1

當使用模板時，實現應該在翻譯單元中（最常見相同的頭文件），它定義了接口。有解決方法，但事實總是存在。

來源

2011-11-22 18:29:44 perreal

你可能想在這好好看看：http://www.amath.unc.edu/sysadmin/DOC4.0/c-plusplus/c%2B%2B_ug/Templates.new.doc.html從這篇文章中，

Because of the separation of header and template source files, you must be very careful in file construction, placement, and naming. You may also need to explicitly identify the location of the source file to the compiler.

來源

2013-12-29 14:29:52

多個文件困難的模板

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