Split cpp file, linked to one .h

[jNc]

have header.h and 0.cpp and 1.cpp, both include header.h, I create object in body of 0.cpp, but it is not visible in 1.cpp

[Ganado]

The keyword to learn here is 'extern', if you're talking about a global variable.

0.cpp:

// global scope
Object g_obj;

header.h:

struct Object { 
    void foo() { }
};

extern Object g_obj;

1.cpp:

#include "header.h"

// use obj
void bar()
{
    g_obj.foo();
}

But, when possible, you should try to avoid using global variables. Pass variables through functions when feasible. This isn't always possible if you're working with low-level things like interrupts/poorly-designed callbacks, but it should be a general guideline to strive towards.

(Side-note: Think I found a bug in the formatting on the website...)

[keskiverto]

Sounds like you aim for global variable. That is almost always unnecessary.

Do show simple case of what you do have. Like:

// header.h
#ifndef header_h
#define header_h

struct Foo {
  int x {};
};

int func( const Foo& f );

#endif


// f0.cpp
#include "header.h"

int main(){
  Foo bar {42};
  int answer = func( bar );
}


// f1.cpp
#include "header.h"

int func( const Foo& f ){
  return f.x;
}

[newbieg]

If you need information on why there's so much hate for global variables, then here's some reading:

The short version:
https://www.tutorialspoint.com/Why-should-we-avoid-using-global-variables-in-C-Cplusplus
An almost fun in-depth version:
https://thevaluable.dev/global-variable-explained/

They may be useful if you are creating a default state for your class (like cin and cout are objects of the iostream class), but it's worth knowing the downsides to using/providing them.

Please apply namespaces if you choose to use global variables.