C++ LNK2005 In Inline File - c++11

Question

As the title suggests, I have an linker error relating to my inline file. It is complaining that my dungeon_layout header that includes my dungeon_room header(which includes the inl file) defines something twice. All my headers have guards, I only include .hpp files, and yet it still gets angry when I try and overload the assignment operator. The code which it complains is such:
Where I need assignment 1:
dungeon_room dungeon_layout::getCurrentRoom()
{
...
dungeon_room temp;
for (row = levelLayout.begin(); row != levelLayout.end(); row++)
{
for (col = row->begin(); col != row->end(); col++)
{
if (col->active)
{
...
temp = *col;
...
}
}
...
}
return temp;
}
Where I need assignment 2:
dungeon_room::dungeon_room()
{
...
roomMap = tim::tileMap(20, 20, 50);
...
}
Assignment Operator 1:
tileMap tim::tileMap::operator=(const tileMap& other)
{
// nothing...
}
Assignment Operator 2:
void dungeon_room::operator=(const dungeon_room& other)
{
// nothing...
}
Header for the Tile Manager (inl file definitions for functions)
#ifndef DUNGEON_ROOM_HPP
#define DUNGEON_ROOM_HPP
...
#include "gridManager\tileManager.hpp"
...
#endif
Header for the level layout
#ifndef DUNGEON_LAYOUT_HPP
#define DUNGEON_LAYOUT_HPP
...
#include "dungeon_room.hpp"
...
#endif
Error:
1>dungeon_room.obj : error LNK2005: "private: void __cdecl
tim::tileMap::addSprite(class sf::RectangleShape,unsigned __int64)" (?addSprite#tileMap#tim##AEAAXVRectangleShape#sf##_K#Z) already defined in dungeon_layout.obj
1>dungeon_room.obj : error LNK2005: "private: void __cdecl tim::tileMap::addSprite(class sf::Sprite,unsigned __int64)" (?addSprite#tileMap#tim##AEAAXVSprite#sf##_K#Z) already defined in dungeon_layout.obj
1>dungeon_room.obj : error LNK2005: "public: void __cdecl tim::tileMap::modifyTile(int,int,int)" (?modifyTile#tileMap#tim##QEAAXHHH#Z) already defined in dungeon_layout.obj
1>dungeon_room.obj : error LNK2005: "public: void __cdecl tim::tileMap::addCollisionValue(int)" (?addCollisionValue#tileMap#tim##QEAAXH#Z) already defined in dungeon_layout.obj
1>dungeon_room.obj : error LNK2005: "public: void __cdecl tim::tileMap::drawTiles(class sf::RenderWindow &,class sf::View &)" (?drawTiles#tileMap#tim##QEAAXAEAVRenderWindow#sf##AEAVView#4##Z) already defined in dungeon_layout.obj
1>dungeon_room.obj : error LNK2005: "public: void __cdecl tim::tileMap::drawTiles(class sf::RenderWindow *,class sf::View &)" (?drawTiles#tileMap#tim##QEAAXPEAVRenderWindow#sf##AEAVView#4##Z) already defined in dungeon_layout.obj
1>dungeon_room.obj : error LNK2005: "public: void __cdecl tim::tileMap::drawTiles(class sf::RenderWindow &)" (?drawTiles#tileMap#tim##QEAAXAEAVRenderWindow#sf###Z) already defined in dungeon_layout.obj
1>dungeon_room.obj : error LNK2005: "public: void __cdecl tim::tileMap::drawTiles(class sf::RenderWindow *)" (?drawTiles#tileMap#tim##QEAAXPEAVRenderWindow#sf###Z) already defined in dungeon_layout.obj
1>dungeon_room.obj : error LNK2005: "public: void __cdecl tim::tileMap::operator=(class tim::tileMap const &)" (??4tileMap#tim##QEAAXAEBV01##Z) already defined in dungeon_layout.obj
1>dungeon_room.obj : error LNK2005: "public: __cdecl tim::tileMap::tileMap(void)" (??0tileMap#tim##QEAA#XZ) already defined in dungeon_layout.obj
1>dungeon_room.obj : error LNK2005: "public: __cdecl tim::tileMap::tileMap(float,float,float)" (??0tileMap#tim##QEAA#MMM#Z) already defined in dungeon_layout.obj
1>F:\Desktop Files\C++\Games\Dungeon_Seeker\x64\Debug\Dungeon_Seeker.exe : fatal error LNK1169: one or more multiply defined symbols found
I believe that this should be the relevant code. I've been stuck, and debugging for a while now, and it's been annoying. Please help, thanks!

Answer 1

The reason you are getting these errors is because the function is being compiled for each .cpp file it has been compiled in, which is then being exported multiple times, once for each .cpp file that includes your inline file.
The .inl file that contains the definition is pasted into each of the .cpp files that includes it. Meaning, when the program is linked together, there is a definition of the function, that was supposed to only be defined once, in several files. This breaks the One Definition Rule and is the reason the linker is giving you that error.
To fix it, you have three options. First, you can mark the functions as inline, which does not necessarily make the compiler inline the function, but allows the function to be defined multiple times. Second, you can move the definition of the function inside the definition of the class, which implicitly marks the functions as inline. Or you can define the function in a .cpp file.
With you code, if you still want to have the functions declared in an .inl file you can put inline in front of the definitions of the function in the error messages. In this case those functions are
tim::tileMap::addSprite
tim::tileMap::modifyTile
tim::tileMap::addCollisionValue
tim::tileMap::drawTiles //All 4 overloads
tim::tileMap::operator=
tim::tileMap::tileMap //Both constructor overloads