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Overview

Apple’s Objective-C compiler allows you to freely mix C++ and Objective-C code in the same source file. This Objective-C/C++ language hybrid is called Objective-C++. With it you can make use of existing C++ libraries from your Objective-C applications. Note that Xcode requires that file names have a “.mm” extension for the Objective-C++ extensions to be enabled by the compiler.

Objective-C++ does not add C++ features to Objective-C classes, nor does it add Objective-C features to C++ classes. For example, you cannot use Objective-C syntax to call a C++ object, you cannot add constructors or destructors to an Objective-C object, and you cannot use the keywords this and self interchangeably. The class hierarchies are separate; a C++ class cannot inherit from an Objective-C class, and an Objective-C class cannot inherit from a C++ class. In addition, multi-language exception handling is not supported. That is, an exception thrown in Objective-C code cannot be caught in C++ code and, conversely, an exception thrown in C++ code cannot be caught in Objective-C code. For more information on exceptions in Objective-C, see “Exception Handling.”

The next section discusses what you can do with Objective-C++.

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