Advanced declarations and includes

Question

When working with a library, be it my own or external, there are many classes with forward declarations. The same classes are also included depending on the situation. When I use a specific class, I need to know if certain objects that the class uses are declared, or if they include #include (d). The reason is because I want to know if I should include both headers or only one.

Now I know that this is pretty simple to check, just compile (or look through all the headers until you find the object in question, either #include (d) or declared ahead). But with large projects, a simple compiler takes a lot of time, and each include file checks to see if the class in question is included or if a delay is announced, but this is tedious, especially if it's several levels. To illustrate the problem further:

Class A is class B, it is class C that has a pointer to class Foo

I turn on class A and want to know if the Foo class is ready to be used right away, or I need to do the following:

#include "ClassA.h"
#include "ClassFoo.h"

So, is there a quick and easy way to find out about this dependency without compiling or going into dependent headers? (one of the reasons why I ask this question is because I want, in the end, to make an add-on for VS and / or a stand-alone program for this, if the functionality does not exist yet)

Thank!

Answer 1

In the source file, you should not depend on what other header files are included.

You must explicitly include all the types your code depends on.
If you are not using a type (i.e., simply passing a pointer or a link around), you do not need to define it, so do not include its header file (the header file for your methods should have at least a forward declaration).

. Foo, "ClassFoo.h", . ( ). , , ( ) .

: . / .

Answer 2

, , -, hella more. . . #include -, , (#includes - ), , ). Foo Bar, Foo.h "Bar.h", forward. Foo.cpp Bar.h.

foo.h

class Bar ; // fwd declare wherever possible

class Foo
{
  // I can haz needs Bar
  void do( Bar *bar ) ;
} ;

foo.cpp

#include "Foo.h"
#include "Bar.h" // I can has needs complete implementation details.

Foo::do( Bar *bar )
{
}

bar.h

class Bar
{
  // code..
} ;

Answer 3

class A, C (, , A). , access Foo , C . Foo, C. Foo C - , , C.h Foo.h, , .