Is there a way to include an objective-c header from a cpp? Because when I try to #include "cocos2d.h" from a cpp .h file, a lot of errors complaining about @'s and -'s are showing up.
Can c++ files include obj-c headers like that?
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1Including a file is just like copying and pasting code from one file to another. I'm not sure why you think this would work since they are different languages. I think the question you should be asking is "how can I interface C++ code with objective C code".Cogwheel– Cogwheel2010-07-18 20:29:09 +00:00Commented Jul 18, 2010 at 20:29
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When using .mm file, Obj-c is just fine including cpp, so I thought the inverse was possible.sharvey– sharvey2010-07-18 20:41:31 +00:00Commented Jul 18, 2010 at 20:41
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Yes, but the inverse is including ObjC in a .mm file that mainly uses C++.Georg Fritzsche– Georg Fritzsche2010-07-18 20:44:43 +00:00Commented Jul 18, 2010 at 20:44
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3 Answers
It is possible, but you need to use Objective-C++ (e.g. by making the file extension .mm) to mix the languages, plain C++ sources don't work.
To make that clear:
.mfiles only allow Objective-C sources.cppfiles only allow C++ sources.mmallow mixed Objective-C++ sources - i.e. both Objective-C and C++ with some limitations
If you need to keep the two worlds seperated instead you need to write wrapper classes that hides the Objective-C details from C++ and vice versa.
answered Jul 18, 2010 at 20:32
Georg Fritzsche
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9 Comments
sharvey
So interfacing with an objective-c library from c++ is impossible? Hopefully not.
Georg Fritzsche
@shar: Technically you can call into ObjC from plain C++ using the runtime functions - but you'll not want to do that. Just use either the mixed approach or wrap the ObjC classes.
sharvey
@Georg Fritzsche: but if I do, seems like I can't use cpp syntax in the .h or .mm file.
Georg Fritzsche
@shar: In the
.mm this should be no problem, you might want to ask about that instead with more details. In the header this is fine as long you don't include it in plain .m files.sharvey
@Georg Fritzsche: I'm currently using a framework which uses .m files. Might that be the problem, and if yes, is there a way to work around it?
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C++ has no idea what Objective-C is. So including an Objective-C .h in a .cpp is a no-go.
The other way around, though is fine, if you use the .mm file extension (Objective-C++) instead of .m (Objective-C).
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Jon Reid
It would be gross, but if you really really wanted to include a header that includes Objective-C in a .cpp, wrap the Objective-C stuff in
#ifdef __OBJC__ … #endif to prevent it from being parsed.It is possible when you are compiling with mixed objc/c++. Cocoa applications can be written in languages mix in both directions: you can either use an obj-c class inside the C++ or a C++ class inside a obj-c object.
I assume in your case you are compiling pure C++ app where the obj-c code is not allowed.
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sharvey
No, i'm developing for iphone os and the cpp header file is referenced from a .mm file.