Objective-C Feature Availability Index-优快云博客

本文详细解析了 Objective-C 语言特性与所需 Xcode 和编译器版本之间的关系，以及它们在不同 OS X 和 iOS 系统上的部署兼容性。

Objective-C Feature Availability Index

This article correlates features of the Objective-C language with the versions of Xcode and compiler you need to use them, and the OS versions you can use them with.

For more information about these modern Objective-C features, see Programming with Objective-C.


Feature	Tools versions	OS X deployment	iOS deployment
Automatic Reference Counting (ARC)	Xcode 4.2 (LLVM Compiler 3.0)	Requires modern runtime Deploys back to OS X v10.7	Deploys back to iOS 5
Automatic Reference Counting without zeroing weak reference (“ARCLite”)	Xcode 4.2 (LLVM Compiler 3.0)	Requires modern runtime Deploys back to OS X v10.6	Deploys back to iOS 4
`@autoreleasepool` blocks	Xcode 4.2 (LLVM Compiler 3.0)	Using ARC: Requires modern runtime and deploys back to OS X v10.6 Using MRR: All releases	Using ARC: Deploys back to iOS 4 Using MRR: All releases
Default synthesis of `@property` instance variables and accessor methods	Xcode 4.4 (LLVM Compiler 4.0)	Requires modern runtime	Deploys back to iOS 4
Instance variables in class extensions and `@implementation` block	Xcode 4.2 (LLVM Compiler 3.0)	Requires modern runtime	All iOS releases
No forward method prototypes needed in `@implementation` block	Xcode 4.3 (LLVM Compiler 3.1)	All releases	All iOS releases
`NSNumber`, `NSDictionary` and `NSArray` literals	Xcode 4.4 (LLVM Compiler 4.0)	All releases	All iOS releases
`@YES` and `@NO` literals	Xcode 4.4 and OS X 10.8 or later SDK Xcode 4.5 and iOS 6.0 or later SDK (LLVM Compiler 4.0)	All releases	All iOS releases
`NSDictionary` and `NSArray` subscripting	Xcode 4.4 and OS X 10.8 or later SDK Xcode 4.5 and iOS 6.0 or later SDK (LLVM Compiler 4.0)	Requires modern runtime Deploys back to OS X v10.6	Deploys back to iOS 5