Objective-C Feature Availability Index に一覧表が載ってるのですが、ARCのWeak Reference 以外は iOS 4 以上、ほとんどはすべての iOS バージョンで動くので、古い環境を気にせずにジャンジャン使ってしまってOKです。
新しいリテラルや Subscripting は断然コードが書きやすく読みやすくなるのでこれはうれしいですね。
Objective-C Feature Availability Index
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 |
Default synthesis of @property instance variables and accessor methods | Xcode 4.4 (LLVM Compiler 4.0) | Requires modern runtime Deploys back to OS X v10.6 | Deploys back to iOS 4 |
Instance variables in class extensions | Xcode 4.2 (LLVM Compiler 3.0) | Requires modern runtime | All iOS releases |
Instance variables in @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 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 or later SDK (LLVM Compiler 4.0) | Requires modern runtime Deploys back to OS X v10.6 | Deploys back to iOS 4 |