error LNK2019: unresolved external symbol vs2013 [duplicate] - c++

Question

This question already has answers here:
What is an undefined reference/unresolved external symbol error and how do I fix it?
(39 answers)
Closed 6 years ago.
I get this error, but I don't know how to fix it.
I'm using Visual Studio 2013.
code
-----DateUtils.h
#pragma once
#include <string>
class DateUtils
{
public:
DateUtils();
~DateUtils();
static time_t str2time_t(const std::string&, const std::string&);
};
-----ForexUtils32.h
#include <string>
// The following ifdef block is the standard way of creating macros which make exporting
// from a DLL simpler. All files within this DLL are compiled with the FOREXUTILS32_EXPORTS
// symbol defined on the command line. This symbol should not be defined on any project
// that uses this DLL. This way any other project whose source files include this file see
// FOREXUTILS32_API functions as being imported from a DLL, whereas this DLL sees symbols
// defined with this macro as being exported.
#ifdef FOREXUTILS32_EXPORTS
#define FOREXUTILS32_API __declspec(dllexport)
#else
#define FOREXUTILS32_API __declspec(dllimport)
#endif
// This class is exported from the ForexUtils32.dll
class FOREXUTILS32_API CForexUtils32 {
public:
CForexUtils32(void);
// TODO: add your methods here.
};
extern FOREXUTILS32_API int nForexUtils32;
FOREXUTILS32_API int fnForexUtils32(void);
/******************** Add Begin *************************/
FOREXUTILS32_API time_t str2time(const std::string&, const std::string&);
/******************** Add End *************************/
-------DateUtils.cpp
#include "stdafx.h"
#include "DateUtils.h"
#include <sstream>
#include <iomanip>
using namespace std;
DateUtils::DateUtils()
{
}
DateUtils::~DateUtils()
{
}
time_t str2time_t(const string& datetimeIn, const string& formatIn) {
struct tm tm_time;
// For C++11
istringstream iss(datetimeIn);
iss >> get_time(&tm_time, formatIn.c_str());
time_t time = mktime(&tm_time);
return time;
}
------ForexUtils32.cpp
// ForexUtils32.cpp : Defines the exported functions for the DLL application.
//
#include "stdafx.h"
#include "ForexUtils32.h"
#include "DateUtils.h"
// This is an example of an exported variable
FOREXUTILS32_API int nForexUtils32=0;
// This is an example of an exported function.
FOREXUTILS32_API int fnForexUtils32(void)
{
return 42;
}
// This is the constructor of a class that has been exported.
// see ForexUtils32.h for the class definition
CForexUtils32::CForexUtils32()
{
return;
}
/******************** Add Begin *************************/
FOREXUTILS32_API time_t str2time(const std::string& datetime, const std::string& format)
{
time_t t = DateUtils::str2time_t(datetime, format);
return t;
}
/******************** Add End *************************/
Error message:
Error 1 error LNK2019: unresolved external symbol "public: static
__int64 __cdecl DateUtils::str2time_t(class std::basic_string,class
std::allocator > const &,class std::basic_string,class std::allocator > const &)"
(?str2time_t#DateUtils##SA_JABV?$basic_string#DU?$char_traits#D#std##V?$allocator#D#2##std##0#Z) referenced in function "__int64 __cdecl str2time(class
std::basic_string,class
std::allocator > const &,class std::basic_string,class std::allocator > const &)"
(?str2time##YA_JABV?$basic_string#DU?$char_traits#D#std##V?$allocator#D#2##std##0#Z) D:\visual
studio
2013\Projects\32bit\ForexUtils32\ForexUtils32\ForexUtils32.obj ForexUtils32
How can i fix this error ?Help me Please(I'm not good at english very much. Thanks)

Answer 1

The first line of the function definition
time_t str2time_t(const string& datetimeIn, const string& formatIn) {
have to be
time_t DateUtils::str2time_t(const string& datetimeIn, const string& formatIn) {
(Add the class name to which the member function belongs)