Adopting Modern Objective-C

• Change id to instancetype in appropriate places

• Change enum to NS_ENUM or NS_OPTIONS

  • The NS_ENUM macro helps define both the name and type of the enumeration, in this case named UITableViewCellStyle of type NSInteger. The type for enumerations should be NSInteger.

• Update to the @property syntax

• Converting to literals, so a statement like [NSNumber numberWithInt:3] becomes @3.

• Using subscripting, so a statement like [dictionary setObject:@3 forKey:key] becomes dictionary[key] = @3.

Adopting Modern Objective-C

原文：http://www.cnblogs.com/littlepony/p/6427974.html