[iOS]Objective-C 实用特性索引（Objective-C Feature Availability Index）

Objective-C 实用特性索引（Objective-C Feature Availability Index）

本文档分别针对 Xcode 版本以及使用的编译器，还有使用的操作系统版本，将 Objective-C 的各种特性串联起来。

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.

特性 Feature	工具版本 Tools versions	OS X 部署版本 OS X deployment	iOS 布署版本 iOS deployment
自动引用计数 (ARC) 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
无归零弱引用的自动引用计数(“ARCLite”) 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
默认合成 @property 的实例变量和访问器方法 Default synthesis of @property instance variables and accessor methods	Xcode 4.4 (LLVM Compiler 4.0)	Requires modern runtime	Deploys back to iOS 4
实例变量声明于类扩展中 Instance variables in class extensions	Xcode 4.2 (LLVM Compiler 3.0)	Requires modern runtime	All iOS releases
实例变量声明于 @implementation 实现块 Instance variables in @implementation block	Xcode 4.2 (LLVM Compiler 3.0)	Requires modern runtime	All iOS releases
@implementation 实现块中无需前向方法原型声明 No forward method prototypes needed in @implementation block	Xcode 4.3 (LLVM Compiler 3.1)	All releases	All iOS releases
NSNumber, NSDictionary 和 NSArray 字面值 NSNumber, NSDictionary and NSArray literals	Xcode 4.4 (LLVM Compiler 4.0)	All releases	All iOS releases
布尔值 @YES 和 @NO 字面值 @YES and @NO literals	Xcode 4.4 and OS X 10.8 or later SDK Xcode 4.5 and iOS 6 or later SDK (LLVM Compiler 4.0)	All releases	All iOS releases
NSDictionary 和 NSArray 下标 NSDictionary and NSArray subscripting	Xcode 4.4 and OS X 10.8 or later SDK Xcode 4.5 and iOS 6 or later SDK (LLVM Compiler 4.0)	Requires modern runtime Deploys back to OS X v10.6	Deploys back to iOS 4

• “需要现代的运行时” 暗指 64 位系统。

  “Requires modern runtime” implies 64-bit systems.