Unresolved external symbol on non-inline function body - c++

Question

These type of errors are well discussed on SO and many other places, yet, I couldnt find a solution to my particular case.
Basically, I have made a static library project in my solution to seperate some functionality, and reference it in my current project. When I try to call a function from the library, i got this notorious linker error. I think there are no problems in setting up the project (references, dependencies etc.) .
First, I will give some minimal example of what I am working on ( there are some third party classes )
//FileReader.h
class IBKFileReader{
public:
virtual ~IBKFileReader() {} ;
virtual void readFile(std::string fileName, pcl::PointCloud<pcl::PointXYZ>::Ptr pointCloud ) = 0 ;
};
class XYZFileReader : public IBKFileReader
{
public:
virtual void readFile(std::string fileName, pcl::PointCloud<pcl::PointXYZ>::Ptr pointCloud )
{
}
And in my code, I call readFile function on a IBKFileReader object polymorphically.
And, this part is ok, without any errors, it compiles, links and runs.
However, when I move the body of the readFile function to a .cpp file and implement it there
(with the same signature hopefully, i copy pasted) , I got the unresolved external symbol error. This is the header of the function in .cpp file.
void XYZFileReader::readFile(std::string fileName, pcl::PointCloud<pcl::PointXYZ>::Ptr pointCloud )
It seems that implementing the function body inline in the header file, and implementing in some seperate file makes a difference.
What do you think of this issue? Has anybody experienced something similar to this? I hope I am not missing out something obvious.
EDIT:
This is the error log i get:
1>main.obj : error LNK2001: unresolved external symbol "public: virtual void __cdecl XYZFileReader::readFile(class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> >,class boost::shared_ptr<class pcl::PointCloud<struct pcl::PointXYZ> >)" (?readFile#XYZFileReader##UEAAXV?$basic_string#DU?$char_traits#D#std##V?$allocator#D#2##std##V?$shared_ptr#V?$PointCloud#UPointXYZ#pcl###pcl###boost###Z)
EDIT:
I may have caused some misunderstanding.
FileReader.h and FileReader.cpp is in static library project. I didnt do more than just implementing the function in the cpp file, definitions and such are still there.
In the same solution, in another project I reference to this project.
I am not getting the linker error when compiling the static lib, but when I am using it.
Sorry for my bad English.

Answer 1

A member function that is defined inside its class member list is called an inline member function. Try moving the member definition out of the class definition.
class XYZFileReader : public IBKFileReader
{
public:
virtual void readFile(std::string fileName,
pcl::PointCloud<pcl::PointXYZ>::Ptr pointCloud);
};
void XYZFileReader::readFile(std::string fileName,
pcl::PointCloud<pcl::PointXYZ>::Ptr pointCloud) {}