Why do we make headers and cpp files and then include them in main.cpp like file.h and file.cpp and then #include "file.h" in the main.cpp, and if I'm creating a class should I do the same thing whats best practice in this case ?
#Clean code advice
distant apex
viral grottoBOT
burnt surge
Why do we make headers and cpp files and then include them in main.cpp like file...
- don't
#include "file.cpp", you should include headers not source files (except in very specific circumstances) - you don't necessarily need a unique header file and source file for every class, there isnt a best practice on this its just whatever coding style your project uses. I often have multiple types + functions per header (and then implement them in an equivalent source file)
headers and cpp files dont necessarily related to using classes or not
its about functions
(classes can have member functions but theyre treated similarly with regards to linking and ODR)
distant apex
So classes don't really need to be in individual header files same goes for the member functions inside of them, and we cpp #include "file.h" in the main.cpp not the cpp file.
burnt surge
void foo() {
// ...
}
```this is a function definition. The c++ standard is always using weird termonology so im just going to say lets call `foo` an "entity"
C++ has something called the one definition rule (ODR) which means that every entity can have at most 1 definition. You can't have a definition for `foo` in 1 cpp file and another definition for `foo` in another cpp file because then how would c++ know which is the correct `foo`
If you put a definition in a header and then include that header in multiple places you create multiple definitions which violates ODR
This is true for every entity. So if you have a class `C` with functions `a` and `b` like
```cpp
class C {
void a();
static void b();
};
```then there can only be 1 definition of `C::a` and `C::b`. This is where a cpp file would come in handy. You would define these as
```cpp
void C::a() {
// ...
}
void C::b() {
// ...
}
```in a cpp file and not in the header (since every file that included that header would be making a duplicate definition)
bitter flame
So classes don't really need to be in individual header files same goes for the ...
we split them in separate files to speed up the build process, not for code quality lmao
distant apex
we split them in separate files to speed up the build process, not for code qual...
Oh
bitter flame
its not for speeding up the build process
avoiding re-building unchanged source files? obviously?
burnt surge
the concepts of headers and cpp files makes the build process slower
bitter flame
when compiling?
burnt surge
it was designed that way because of limited resources
its not for speed
its actually a terrible way to compile
which is why everything nowerdays uses modules-like systems
bitter flame
which is why everything nowerdays uses modules-like systems
so you are telling me that in a small project with 50 cpp files, when I edit only one of these, I should recompile the remaining 49? are you serious? of course you won't recompile the other 49
burnt surge
so you are telling me that in a small project with 50 cpp files, when I edit onl...
no but thats not why it was desigend that way
thats a happy side effect
and also not always true
bitter flame
thats a happy side effect
a.k.a. the objective
burnt surge
no
its not the objective
as I said
its not why it was designed that way
its designed that way because early pcs were very memory constrained
and splitting the build into multiple steps was the only way to do it and actually have a functioning compiler
burnt surge
so you are telling me that in a small project with 50 cpp files, when I edit onl...
you also don't need to recompile source files in module-based systems if you can prove none of the related modules changed. its not a different idea
bitter flame
and splitting the build into multiple steps was the only way to do it and actual...
okay, the compiler consumes loads of RAM, so you split the work, I get that part
distant apex
```cpp
void foo() {
// ...
}
```this is a function definition. The c++ standar...
I perfectly understood this but I have no clue what you guys are saying, so what is the best-practice should I do different cpp and header files or put them all in the main.cpp
burnt surge
I perfectly understood this but I have no clue what you guys are saying, so what...
you should likely use different cpp files for your implementations than main
bitter flame
I perfectly understood this but I have no clue what you guys are saying, so what...
that's fine, careful not to hit cyclical includes, they need forward declaration magic to resolve them
burnt surge
usually we reserve main for the program's user interface/startup code
or higher levels of abstraction
distant apex
Perfect understood, thank you guys for your assistance ❤️
viral grottoBOT
@distant apex Has your question been resolved? If so, type !solved :)
distant apex
!solved
viral grottoBOT
hoary skiff
!solved
Hey i think you and i are on same page beginner right! Can you tell me from where you're studying
bitter flame
Any server for that
mostly from learncpp.com
distant apex
Hey i think you and i are on same page beginner right! Can you tell me from wher...
To be honest not a single place I just keep doing projects and whenever I'm stuck with something I search google then as my last solution I come ask people here, learncpp.com is good and also if you're an absolute beginner CodingWithMosh on youtube is good aswell thats where I started.
hoary skiff
To be honest not a single place I just keep doing projects and whenever I'm stuc...
Thanks I'm also a newbie