Including headers and Main.h [closed]

Question

Ok not sure if this is the right way or even a correct way but i have seen this and started to use it, Say you have 6 files

main.cpp
main.h

car.cpp
car.h

speed.cpp
speed.h

• 1st - should you ever have a main.h?
• 2nd - if main.h has #include car.h and #include speed.h then in car/speed.cpp do you just have to add #main.h (thus it would include car/speed.h)
• 3rd - should you ever go that route?

Answer 1

#include minimalistically. The reason behind an include should be that, if removed, the code doesn't compile.

Don't #include when you can forward-declare. If "Class A;" will suffice, don't #include a.h.

In particular, prefer to forward-declare in header files, avoiding nested includes which generate highly coupled mega-include files.

See also Self-sufficient header files, in a related question.

Answer 2

1) Only if you need to expose something in main.cpp to other cpp files, so depends on what it has.

2) Possible but not recommended.

3) For a number of reasons (code design, compile time, etc), you want to include as little as needed. Additionally, its convention for your class to have a .h and a .cpp and for one to directly include the other. You should also try to include headers in your .cpp files, and try to avoid headers including headers where possible.