__OBJC__ in objective C

Question

What does __OBJC__ mean in Objective C?

#import 

#ifdef __OBJC__
    #import 
    #import <         


        

Answer 1

It means the objective C compiler is being used. So you can create hybrid header files that can be used when compiling objective C or C or C++.

You could use it in a header file like this, if you wanted to publish a header file that defined an objective c object that you wanted to make available to c and c++ programmers/code :

#ifndef MYHEADER_H
#define MYHEADER_H

#ifdef __OBJC__
// Put objective C things in this block
// This is an objc object implemented in a .m or .mm file
@implementation some_objc_object {
}
@end
#endif

#ifdef __cplusplus
#define CLINKAGE "C"
// c++ things that .m or .c files wont understand go in here
// This class, in a .mm file, would be able to call the obj-c objects methods
// but present a c++ interface that could be called from c++ code in .cc or .cpp 
// files
class SomeClassThatWrapsAnObjCObject
{
  id idTheObject;
public:
  // ...
};
#endif
// and here you can declare c functions and structs
// this function could be used from a .c file to call to a .m file and do something
// with the object identified by id obj
extern CLINKAGE somefunction(id obj, ...); 
#endif // MYHEADER_H