c++ - 创建一个只有模板头文件的项目库文件

Question

我的 C++ 项目完全基于模板，因此我的代码被拆分到不同的头文件中(只有头文件的项目)。但是我想为库的用户提供一个头文件(“库文件”)，他们必须包含才能使用该库。一种可能性是手动将所有代码复制到一个文件中，但如果项目更大，我想使用 make 自动创建文件。 .所以我的想法是设置库文件，我在其中包含所有源文件并使用 g++ -E 处理它(只是预处理)。但是预处理器无论如何都会将内容包含的文件写入多个文件(即 <string> )，也多次写入输出文件。当我使用该库时，这会导致“多重定义”错误。

那么是否有可能阻止多次复制，或者是否有另一种方法可以用来实现我获取一个库文件的目标？

如果您需要一些示例代码来回答问题，请发表评论。

例子:

标题.h:

#ifndef CSV_H_
#define CSV_H_

#include <deque>
#include <istream>
#include <string>

using std::deque;
using std::istream;
using std::string;

namespace csv {

template<typename T>
class csv_parser {
private:
    deque<T> line;
public:
    template<typename S>
    friend csv_parser<S>& operator>> (istream& input, csv_parser<S>& parser); //file input stream operator
    deque<T>& operator>> (deque<T>& target); //data output operator
    deque<T> get_line(); //get parsed line
    void set_line(string input);  //set line and parse
};
#endif

定义.h:

#include <deque>
#include <istream>
#include <sstream>
#include <string>
#include <algorithm>
#include "../headers/csv.h"

using std::deque;
using std::istream;
using std::stringstream;
using std::string;
using std::getline;
using std::copy;

namespace csv {

template<typename T>
csv_parser<T>& operator>> (istream& input, csv_parser<T>& parser) {
    parser.line.clear(); //clear the data
    T buffer;
    string line;
    stringstream converter;

    getline(input, line); //get one line from csv file

    while (line.size() > 0) { //get field from csv line and delete this segment until
                              //input line is empty
        if (line.find_first_of(",") != -1) { //(not the last segment [one ',' left])
            converter << line.substr(0, line.find_first_of(",")); //add segment to converter
            converter >> buffer; //convert segment to T type
            converter.clear(); //clear flags of converter (normally EOF flag is set
                                //after converting), so writing in converter is enabled again
            parser.line.push_back(buffer); //write segment into data
            line.erase(0, line.find_first_of(",")+1); //delete segment from input line
        }
        else { //(last segment in line)
            converter << line.substr(0, line.length()); //get rest of the line
            converter >> buffer; //convert segment to T type
            converter.clear(); //clear flags of converter (normally EOF flag is set
                               //after converting), so writing in converter is enabled again
            parser.line.push_back(buffer);//write segment into data
            line.erase(0, line.length()); //delete rest of input string
        }
    }
    return parser;
}

template<typename T>
void csv_parser<T>::set_line(string input) {
    line.clear();
    T buffer;
    stringstream converter;

    while (input.size() > 0) { //get field from input and delete this segment until
                              //input is empty
        if (input.find_first_of(",") != -1) { //(not the last segment [one ',' left])
            converter << input.substr(0, input.find_first_of(",")); //add segment to converter
            converter >> buffer; //convert segment to T type
            converter.clear(); //clear flags of converter (normally EOF flag is set
                                //after converting), so writing in converter is enabled again
            line.push_back(buffer); //write segment into data
            input.erase(0, input.find_first_of(",")+1); //delete segment from input
        }
        else { //(last segment in line)
            converter << input.substr(0, input.length()); //get rest of the input
            converter >> buffer; //convert segment to T type
            converter.clear(); //clear flags of converter (normally EOF flag is set
                               //after converting), so writing in converter is enabled again
            line.push_back(buffer);//write segment into data
            input.erase(0, input.length()); //delete rest of input
        }
    }
}

template<typename T>
deque<T>& csv_parser<T>::operator>>(deque<T>& target) {//write parsed data into target
    target.clear();
    target.assign(line.begin(), line.end()); //copy data into target
    line.clear(); //delete data
    return target;
}

template<typename T>
deque<T> csv_parser<T>::get_line(){ //return data
    deque<T> buffer = line; //copy data into buffer
    line.clear(); //delete data
    return buffer; //return buffer
}

}

(未编译)library.h:

#include "header.h"
#include "definition.h"

编译指令:

g++ -E library.h -o library_out.h

因此，如果我在应用程序中使用 library_out.h，作为 deque header 一部分的符号将被定义多次。

Answer 1

与其将所有头文件的内容复制到一个巨大的头文件中，不如考虑使用#include 语句。

我的图书馆.h:

#include "myfile1.h"
#include "myfile2.h"
#include "myfile3.h"