extern struct

http://stackoverflow.com/questions/3266580/extern-struct

I'm using extern to fetch variables from another class, and it works fine for int's, float's etc...
But this doesn't work, and I don't know how to do it:

Class1.cpp

struct MyStruct {
 int x;
}

MyStruct theVar;

Class2.cpp

extern MyStruct theVar;

void test() {
 int t = theVar.x;
}

It doesn't work because Class2 doesn't know what MyStruct is.
How do I fix this? :/
I tried declaring the same struct in Class2.cpp, and it compiled, but the values were wrong.

7 down vote accepted

You put the struct MyStruct type declaration in a .h file and include it in both class1.cpp and class2.cpp. IOW: Myst.h struct MyStruct { int x; };   Class1.cpp #include "Myst.h" MyStruct theVar;   Class2.cpp #include "Myst.h" extern struct MyStruct theVar; void test() { int t = theVar.x; }