Compiling Source Code Conditionally for iOS App 模拟器条件编译，判断是IOS还是MAC

Listing 2-1  Determining whether you’re compiling for a simulator

// Set hello to "Hello, <device or simulator>"!

#if TARGET_IPHONE_SIMULATOR

   NSString *hello = @"Hello, iOS Simulator!";

#else

   NSString *hello = @"Hello, iOS device!";

#endif

Listing 2-2 shows how to use the TARGET_OS_IPHONE macro in a source file to be shared between Mac OS X and iOS.

Listing 2-2  Determining whether you’re compiling for a device

#if TARGET_OS_IPHONE

   #import <UIKit/UIKit.h>

#else

   #import <Cocoa/Cocoa.h>

#endif

The TARGET_OS_IPHONE and TARGET_IPHONE_SIMULATOR macros are defined in the TargetConditionals.h header file.