我正在尝试将我编写的程序拆分为两个源文件，但是我无法链接它们并且错误消息对我没有任何意义。
我将提供相关信息的缩短版本文件：
//grandiose.cpp:
#include "thingy.h"
int main() {}
//thingy.h:
#include<string>
int add (int x, int y);
char * parse_input_fragment(const string & ,const string & , size_t &, size_t &);
//thingy.cpp:
#include "thingy.h"
int add (int x, int y)
{
return x+y;
}
char * parse_input_fragment(const string & objective,const string & input, size_t & first_finder, size_t & second_finder) {
char * string_to_int_buffer = new char[64];
first_finder = input.find(objective, first_finder);
first_finder = (input.find('=', first_finder))+1;
second_finder = input.find(';', first_finder);
int y = 0;
for(unsigned int x = first_finder; x < second_finder; x++) {
if ( (input[x] != ' ') && (input[x] != '\n') ) {
string_to_int_buffer[y] = input[x];
y++;
}
}
string_to_int_buffer[y] = '\0';
first_finder = second_finder;
return string_to_int_buffer;
}
如果我把它放在grandiose.cpp中，那么parse_input_fragment函数编译得很好但是当我按照描述将它拆分时我收到错误消息。我为测试目的添加了“添加”功能，并且编译好了。
我得到的错误消息是thingy.h中的原型： 错误C4430：缺少类型说明符 - 假定为int。注意：C ++不支持default-int
它清楚地标记为字符指针返回类型，并且在没有从grandiose.cpp中拆分时起作用，所以我对这里的问题感到很困惑。
修改
好的，移动using namespace std后;到适当的地方，并包括标题警卫按照建议那些错误消息消失但我得到新的，我进一步困惑。我将包含完整的文件和错误消息。
错误讯息： province.obj：错误LNK2005：“public：__thiscall province :: province（void）”（?? 0province @@ QAE @ XZ）已在grandiose.obj中定义
province.obj：错误LNK2005：“public：__ thiscall province :: province（class std :: basic_string，class std :: allocator＆gt;，int * const）”（?? 0province @@ QAE @ V？$ basic_string @DU？$ char_traits @ D @ std @@ V？$ allocator @ D @ 2 @@ std @@ QAH @ Z）已在grandiose.obj中定义
// grandiose.cpp : Defines the entry point for the console application.
//
#include "stdafx.h"
#include <vector>
#include <ctime>
#include <iostream>
#include <fstream>
#include <string>
#include "market.h"
int _tmain(int argc, _TCHAR* argv[])
{
market England;
ifstream reader;
reader.open ("provinces.txt", ios::in);
if (reader.is_open()) { //check if txt file successfully opened
cout << "\n\nprovinces.txt was successfully opened.\n\n";
}
else {
cout << "\n\nfile was not successfully opened.\n\n";
return (1);
}
string reader_buffer;
while ( reader.good() ) { // while not end of file
getline (reader, reader_buffer, '}'); // get one province's worth of data from txt file
if (!reader_buffer.empty()) {
parse_provinces (reader_buffer); // send data to be parsed
}
}
add(1,2);
return 0;
}
//market.h
#include <iostream>
#include <list>
#include "province.h"
using namespace std;
class market
{
public:
list<province> provinces;
};
//province.h
#ifndef PROVINCE_H
#define PROVINCE_H
#include <iostream>
#include <string>
using namespace std;
int add (int x, int y);
char * parse_input_fragment(const string & ,const string & , size_t &, size_t &);
class province
{
public:
province::province();
province::province(string, int[]);
unsigned int * rural_poor;
unsigned int * urban_poor;
unsigned int * max_mine_jobs;
unsigned int * max_farm_jobs;
unsigned int * employed_mine;
unsigned int * employed_farm;
unsigned int * employed_factory;
string name;
};
province::province () {
rural_poor = new unsigned int(0);
urban_poor = new unsigned int(0);
max_mine_jobs = new unsigned int(0);
max_farm_jobs = new unsigned int(0);
employed_mine = new unsigned int(0);
employed_farm = new unsigned int(0);
employed_factory = new unsigned int(0);
name = "";
}
province::province (string name, int numbers[]) {
province::name = name;
cout << "This province is named " << province::name << endl;
rural_poor = new unsigned int(numbers[0]);
cout << "Rural poor = " << *rural_poor << endl;
urban_poor = new unsigned int(numbers[1]);
cout << "Urban poor = " << *urban_poor << endl;
max_mine_jobs = new unsigned int(numbers[2]);
cout << "Max mine jobs = " << *max_mine_jobs << endl;
max_farm_jobs = new unsigned int(numbers[3]);
cout << "Max farm jobs = " << *max_farm_jobs << endl;
}
province * parse_provinces(string);
#endif
//province.cpp
#include "stdafx.h"
#include "province.h"
int add (int x, int y)
{
return x+y;
}
char * parse_input_fragment(const string & objective,const string & input, size_t & first_finder, size_t & second_finder) {
char * string_to_int_buffer = new char[64];
first_finder = input.find(objective, first_finder);
first_finder = (input.find('=', first_finder))+1;
second_finder = input.find(';', first_finder);
int y = 0;
for(unsigned int x = first_finder; x < second_finder; x++) {
if ( (input[x] != ' ') && (input[x] != '\n') ) {
string_to_int_buffer[y] = input[x];
y++;
}
}
string_to_int_buffer[y] = '\0';
first_finder = second_finder;
return string_to_int_buffer;
}
province * parse_provinces(string input) {
size_t first_finder;
size_t second_finder;
char * string_to_int_buffer;
int population_info[4];
// find the name
first_finder = input.find('=');
string name;
for(unsigned int x = 0; x < first_finder; x++) {
if ((input[x] != ' ') && (input[x] != '\n')) {
name.push_back(input[x]);
}
}
// find the rural poor
string_to_int_buffer = parse_input_fragment("rural_poor", input, first_finder, second_finder);
population_info[0] = atoi(string_to_int_buffer);
// find the urban poor
string_to_int_buffer = parse_input_fragment("urban_poor", input, first_finder, second_finder);
population_info[1] = atoi(string_to_int_buffer);
// find max mine jobs
string_to_int_buffer = parse_input_fragment("max_mine_jobs", input, first_finder, second_finder);
population_info[2] = atoi(string_to_int_buffer);
// find max farm jobs
string_to_int_buffer = parse_input_fragment("max_farm_jobs", input, first_finder, second_finder);
population_info[3] = atoi(string_to_int_buffer);
delete[] string_to_int_buffer;
string_to_int_buffer = NULL;
province * current_province = new province(name, population_info);
return current_province;
}
答案 0 :(得分：2)
即使您包含<string>，您还需要使用std命名空间来访问string类型：
#include<string>
using namespace std;
类型string驻留在std命名空间中，因此只需键入string就不会命名已知类型。
或者，您可以在标头中用string替换std::string的所有出现，并使用.cpp中的using语句（实际上，这是所需的处理方式，因为它避免使用所有std函数和全局命名空间进行调整。
Jason的回答也是一个很好的建议：使用包含保护来保护你的标题，所以如果你包含相同的标题twise（例如间接），你将不会因多个定义而产生编译器错误（C ++有一个定义规则） ：所有类只能定义一次）。这在你的具体情况下不是问题，但是养成避免后期问题的习惯是好事
答案 1 :(得分：0)
当您开始包含多个文件时，您应该在头文件的顶部放置一个预处理器防护，以防止它们被包含两次并导致解析错误。例如，您应该在所有标题中放置以下内容：
//first thing at the top of the header
#ifndef THINGY_H
#define THINGY_H
//...the actual header code
//the very last line of the header
#endif //THINGY_H
这样，如果在代码模块的编译过程中你最终将头文件包含两次，那么预处理器就已经定义了头文件保护令牌，因此，不会包含第二个副本的代码标题。
答案 2 :(得分：0)
将您的实现移动到标头中的cpp文件或内联实现的构造函数/方法，以解决链接器错误。