Namespaces: How to "Object Orientate" them?

[harryhaaren]

Hi everyone,

Im working on a large scale audio program, and I got a question regarding namespaces:

The main() part of the program includes my own headers, each named according to what part it plays in the program, eg: Audio.hpp , Midi.hpp etc. These headers will "load" other headers..? Is this illegal? or can the following be done/fixed?

Inside these headers, i will have a "global" namespace. Best way to describe this is:

audio.hpp

namespace Audio
{
	// Audio Include
	#include <iostream>
	int jack_create_client()
	{
	   std::cout << "In jack_create_client() " << std::endl;
	}
}

Code in Engine.cpp

namespace Engine
{
	#include "audio.hpp"
}

Now say i have a main.cpp, and in it is this:

//#include <iostream>	// Uncomment, and it compiles.
#include "engine.hpp"

int main(int argc, char** argv)
{
	Engine::Audio::jack_create_client();
	return 0;
}

However uncommenting that line exposes iostream to the main.cpp file. (in this case its not bad, but if im using some audio processing function, it could name-clash with a similar function for midi.)

Any Idea how i can call jack_create_client() in a similar way to Engine::Audio::jack_create_client() without this problem??

Hope i made the question clear, i realize its a little complex to explain!
-Harry

[Ancient Dragon]

>>These headers will "load" other headers..? Is this illegal?
Yes. Many standard system header files include other header files.

>>in this case its not bad, but if im using some audio processing function, it could name-clash with a similar function for midi.)
There will be no name clashes because that's exactly one of the purposes of namespaces. Everything in <iostream> is in std namespace.

>>Any Idea how i can call jack_create_client() in a similar way to Engine::Audio::jack_create_client() without this problem??

What problem? If jack_create_client() is in global namespace then just call ::jack_create_client() and that will be different then the function with the same name but in namespace Autio.

[harryhaaren]

Hey Dragon,

Thanks for the reply, but the problem is that the above code throws 211 errors on compiling. They're all fixed if I uncomment the #include <iostream> in the main.cpp file.

And i dont understand why, as im #include <iostream> -ing just before i use the function. And (as you mentioned) the whole idea of namespaces is to not have to have <iostream> included in main.cpp as well.

Im at a loss here, sorry! -Harry

[Ancient Dragon]

You'll have to post the code as I'm sure there is another problem.

[harryhaaren]

Hey again,

The code above is the code im trying to make work. Its included as a Microsoft Visual Studio 2005 project file, but otherwise just grab the 3 source files & do whatever it is you do!

However, I just tried the same thing with a different header than <iostream> and its all good & compiling.. is <iostream> something magic that it must be included for some reason? I mean i know its the InputOutputSTREAM...

anyway, ill flag this as solved for now. Im not fully sure on why it wasnt working earlier though! Cheers Dragon, -Harry

Attached is the "old" version that was not compiling for me.. Im on linux using MonoDevelop, so maybe I got the enviroment slightly wobbely... Duno!

[kvprajapati]

namespace A
{
  #include <iostream>
}

You can't include iostream header file into custom namespaces. The problem is that the qualified names inside the namespace would be A::std::cout, but the library would not contain names qualified with the outer namespace.
However, you may declare header file outside the namespace and use using statement inside the custom namespace.

#include <iostream>
namespace A
{
  using namespace std;
}
int main()
{
      A::cout << "\nHello";
     return 0;
}

http://msdn.microsoft.com/en-us/library/xb3bx4w8(VS.71).aspx