When including a C++ header file from an Objective-C header file it has compiling error, iostream not found

Question

TestViewController.h/TestViewController.mm

HelloWorld.h/HelloWorld.cpp

If I include "HelloWorld.h" into TestViewController.mm it compiles well. When I include "HelloWorld.h" into TestViewController.h it prompts an error: 'iostream' file not found.

My HelloWorld.h code is a simple standard cpp file.

#ifndef __MixedCppTest__HelloWorld__
#define __MixedCppTest__HelloWorld__

#include <iostream>
#include <vector>

class HelloWorld {


public:
    HelloWorld();
    ~HelloWorld();
};
#endif /* defined(__MixedCppTest__HelloWorld__) */

Objective-C and C++ are not compatible. You'll need to use Objective-C++. — Mat, May 04 '14 at 10:53
Additional I can change Compile Source As to Objective-c++, but there is another way to solve it?? — Nicholas Xu, May 04 '14 at 10:53

score 1 · Answer 1 · edited May 23 '17 at 12:06

1

you can use macros

#ifdef __cplus
 // TODO Code
#endif

Reference: Link

edited May 23 '17 at 12:06

Community

1
1

answered May 04 '14 at 11:08

abmussani

451
2
10

Thanks, but Which file I mentioned to use these macros? I need use HelloWorld class. – Nicholas Xu May 04 '14 at 11:33
in .h file. I have also put the reference link. Please visit it. – abmussani May 04 '14 at 12:43
1

it should be `__cplusplus` – Bryan Chen May 07 '14 at 05:17
Thank your solution, but I wanna use some enum in this cpp file.It only works in some time. It's not the problem's essence. – Nicholas Xu May 07 '14 at 09:44
So hide the C++ standard library classes within the `.mm` file and don't mention them in the `.h` file. Create an enumeration semantic that doesn't use the C++ standard library semantics. – trojanfoe May 07 '14 at 09:45

score 0 · Accepted Answer · answered May 07 '14 at 05:11

0

When I include "HelloWorld.h" into TestViewController.h it prompt error: 'iostream' file not found….

Is there any Objective-C files which imports TestViewController.h? At the stage of preprocessing header file becomes a part(along with the source file) of a translation unit, and if you're asking to include such header (with c++ libraries inclusion and c++ class definition) to Objective-C source file - then no, it's impossible. If you searching a way to compile and link .cpp and .m source files to one binary, you could make .mm wrapper unit to wire them together.

answered May 07 '14 at 05:11

bigblackdot

138
1
9

The key is if you import cpp file indirectly, you should change all files to objective-c++ compiled mode on the import chain. My problem is AppDelegate.m is not be changed to .mm – Nicholas Xu May 07 '14 at 09:48
Are you trying to solve any specific problem or just making a reconnaissance? In the second case it's easy to set yourself an unsolvable task which just do not have to be solved at all. – bigblackdot May 07 '14 at 10:34

score 0 · Answer 3 · edited May 23 '17 at 11:48

0

Thanks https://stackoverflow.com/users/635608/mat 's answer.

It has only one standard solution, that's make compiler knows about specified sources should be compiled as objective-c++.

There are only 3 ways:

change .m to .mm
change Type to Objective-c++ in Utilities panel in xcode editor.
change "Compile sources as" to objective-c++

If you import cpp file indirectly, you should change all files to objective-c++ compiled mode on the import chain.

edited May 23 '17 at 11:48

Community

1
1

answered May 07 '14 at 09:40

Nicholas Xu

43
1
5

1

So your solution is to compile all your Objective-C files as Objective-C++? That is a poor solution and better solutions are available. – trojanfoe May 07 '14 at 09:43

When including a C++ header file from an Objective-C header file it has compiling error, iostream not found

3 Answers3