我是C++的新手,只是想做一个涉及3个文件的问题。
我得到了一个带有 namespace 的头文件,该 namespace 声明了一个结构和一些原型(prototype)。在definitions.cpp文件中,我具有所有函数定义。然后main.cpp文件仅创建了一些结构,调用了一些函数来填充结构,然后调用另一个函数来显示结构。
我的问题是它给了我一个无法解决的外部错误。据我所知,我认为编译器抱怨它找不到在main.cpp中调用的函数的原型(prototype)-重载的setStruct()
和showStruct()
。
但是我想当我在main.cpp中包含header.h文件并使用using声明声明函数时,它是否允许编译器访问存储在头文件中的原型(prototype)?
header
#ifndef header_h
#define header_h
namespace SALES
{
const int QUARTERS = 4;
struct Sales
{
double sales[QUARTERS];
double average;
double max;
double min;
};
void setSales(Sales & s, const double ar[], int n);
void setSales(Sales & s);
void showSales(const Sales & s);
}
#endif
Definitions.cpp
#include<iostream>
#include"header.h"
using SALES::Sales;
using SALES::QUARTERS;
double max(Sales & s) //find max sale value in sales array
{
double maxVal = s.sales[0];
for(int i = 1; i<4;i++)
{
if(s.sales[i]>maxVal)
{
maxVal = s.sales[i];
}
}
return maxVal;
}
double min(Sales & s) //find min sale value in sales array
{
double minVal = s.sales[0];
for(int i = 1; i<4;i++)
{
if(s.sales[i]<minVal)
{
minVal = s.sales[i];
}
}
return minVal;
}
void setSales(Sales & s) // fill sales structure interactivly
{
std::cout<< "Please enter the sales for the yearly quarters.\n";
for(int i = 0;i<QUARTERS;i++)
{
std::cout<< "Quater "<<i+1<<": ";
while(!(std::cin>>s.sales[i]))
{
std::cout<<"Please enter valid input\n";
std::cout<< "Quater "<<i+1<<": ";
std::cin.clear();
std::cin.ignore();
}
}
s.average = ((s.sales[0]+s.sales[1]+s.sales[2]+s.sales[3])/4);
s.max = max(s);
s.min = min(s);
}
void setSales(Sales & s, const double ar[], int n) // fill sales structure non interactivly
{
for(int i = 0;i<n;i++)
{
s.sales[i] = ar[i];
}
for(int i = n;i<QUARTERS;i++)
{
s.sales[i] = 0;
}
s.average = ((s.sales[0]+s.sales[1]+s.sales[2]+s.sales[3])/4);
s.max = max(s);
s.min = min(s);
}
void showSales(const Sales & s) // display structure
{
std::cout<< "\nSales for the year\n";
for(int i = 0;i<QUARTERS;i++)
{
std::cout<<"Quarter "<<i+1<<": $"<<s.sales[i];
}
std::cout<<"Max Sale: "<<s.max<<std::endl;
std::cout<<"Min Sale: "<<s.min<<std::endl;
std::cout<<"Average of sales: "<<s.average<<std::endl;
}
Main.cpp
#include<iostream>
#include"header.h"
using SALES::Sales;
using SALES::setSales;
using SALES::showSales;
int main()
{
double Sales1[4] = {453.50, 654.60, 340.20, 500.30};
Sales Year1;
Sales Year2;
setSales(Year1, Sales1, 3);
setSales(Year2);
showSales(Year1);
showSales(Year2);
return 0;
}
错误
1>------ Build started: Project: Myfirst, Configuration: Debug Win32 ------
1> Main.cpp
1>Main.obj : error LNK2019: unresolved external symbol "void __cdecl SALES::setSales(struct SALES::Sales &,double const * const,int)" (?setSales@SALES@@YAXAAUSales@1@QBNH@Z) referenced in function _main
1>Main.obj : error LNK2019: unresolved external symbol "void __cdecl SALES::setSales(struct SALES::Sales &)" (?setSales@SALES@@YAXAAUSales@1@@Z) referenced in function _main
1>Main.obj : error LNK2019: unresolved external symbol "void __cdecl SALES::showSales(struct SALES::Sales const &)" (?showSales@SALES@@YAXABUSales@1@@Z) referenced in function _main
1>E:\Documents\Uni\Programming\C++ starter projects\Myfirst\Debug\Myfirst.exe : fatal error LNK1120: 3 unresolved externals
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========
任何帮助将是巨大的,谢谢。
最佳答案
定义setSales
等函数时,需要告诉编译器它们在SALES namespace 中。推杆
namespace SALES
{
// functions here
}
会做的。
关于c++ - 链接错误2019,原型(prototype)虽然在头文件中,我们在Stack Overflow上找到一个类似的问题:https://stackoverflow.com/questions/22950621/