C++ error C4430 int assumed - c++

Question

I'm a newbie in C++ and have just a small header file in C++ with a simple struct in it.
PGNFinder.h:
#ifndef PGNFINDER_H
#define PGNFINDER_H
struct Field
{
int Order;
string Name;
//more variables but doesn't matter for now
};
#endif
This gives the next errors:
error C2146: syntax error : missing ';' before identifier 'Name'
error C4430: missing type specifier - int assumed. Note: C++ does not support default-int
error C4430: missing type specifier - int assumed. Note: C++ does not support default-int
when I change it to:
struct Field
{
int Order;
std::string Name;
};
It gives a error in the .exe file and the .obj file
error LNK1120: 1 unresolved externals (in the .exe file)
error LNK2019: unresolved external symbol "int __cdecl Convert::stringToInt(class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> >)" (?stringToInt#Convert##YAHV?$basic_string#DU?$char_traits#D#std##V?$allocator#D#2##std###Z) referenced in function "private: void __thiscall CAN::calculateMessageLength(class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> >)" (?calculateMessageLength#CAN##AAEXV?$basic_string#DU?$char_traits#D#std##V?$allocator#D#2##std###Z)
and when I add
#include <string>
and change back to
string Name;
It gives the same errors as in the beginning.
So why can't the header file recognize the int and string?
Thanks for the help :)

Answer 1

In order to use string as type of a variable, you need to
include the header in which it is declared (#include <string>)
use a full qualified type such as std::string or by means of the using directory using namespace std; Note, however, that using is not recommended in header files (see "using namespace" in c++ headers)
If you only try one of these, it won't work.
However, your second error message seems to point to a linker problem.

Answer 2

Since I tend to use the comment function too often.
Your problem is a missing include, and when you included string.h you still forgot the std-namespace of the "string class".
So either use a using namespace std (for beginners best practice, since most stuff will be most likely std stuff)
or declare your string as std::string within your struct.

Answer 3

changing it to std::string clearly fixes the compiler error.
Then you have a linker error which is not related to that line of code. You appear to have a 'Convert' class with a missing implementation of a 'stringToInt' function.