Using Carbon in a Cocoa Application

For a Cocoa application to call Carbon functions, the only requirements are that the compiler has access to the appropriate header files and the application is linked against the appropriate frameworks. To access Carbon functionality, you can simply import Carbon.h and link against the Carbon framework. Since Objective-C is a superset of ANSI C, calling Carbon functions from a Cocoa application is easy (although prior to Mac OS X v10.2 the functions could not be user interface functions).

Using Cocoa in a Carbon Application

A Carbon application, by taking a few extra steps, can use many Cocoa and Objective-C technologies. To access Cocoa functionality, you can simply import Cocoa.h and link against the Cocoa framework. To access other Objective-C technologies, you may need to import additional headers and link against additional frameworks. For example, to use Web Kit, you need to import WebKit.h and link against the WebKit framework.

You also need to take these steps:

• Prepare your Carbon application to use Cocoa by calling the NSApplicationLoad function. Typically, you do this in your main function before executing any other Cocoa code.

• In functions where you’re using Cocoa, allocate and initialize an NSAutoreleasePool object and release it when it is no longer needed. Note that if your application is running in Mac OS X v10.4 or later, an autorelease pool already exists when your functions are called, directly or indirectly, by the toolbox. For example, an NSAutoReleasePool object is automatically established and drained in the following locations:

  • RunApplicationEventLoop

  • RunAppModalLoopForWindow

  • ModalDialog

  • Window drag and resize tracking

  • Control tracking and indicator dragging

  • Across dispatch of an event by the event dispatcher target

  • When a window's compositing views are redrawn

• Use the Objective-C compiler to build those parts of your project that use Cocoa. In Xcode, there are several ways to do this:

  • Use Objective-C filename extensions.

  • Use the File Info panel to set the file type of a source file to sourcecode.c.objc.

  • Change the project or target build setting “Compile Sources As” to Objective-C.

OSStatus changeText (CFStringRef message)

{

    NSAutoreleasePool *localPool;

    localPool = [[NSAutoreleasePool alloc] init];

    [[Controller sharedController] changeText:(NSString *)message];

    [localPool release];

    return noErr;

}