. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167 11.10Enumeration in Objective-C classes . . . . . . . . . . . . . . . . . . . . . . . . . . 167 12 Expressions 169 12.1 Expression Objective-C-related constructs. There are two kinds of Objective-C language features, discerned by a version number: Objective-C 1.0 and Objective-C 2.0. The Objective-C 1.0 language features can be enabled by adding the compiler. The Objective-C 2.0 language features can be enabled using a similar modewitch: {$modeswitch objectivec2} or the command-line option -Mobjectivec2. The Objective-C 2.0 language features

cannot be used in interfaces, Objective-C protocols and categories because all methods of an interface/protocol/- category must be public. Error: An interface, helper or Objective-C protocol or category cannot cannot contain fields Declarations of fields are not allowed in interfaces, helpers and Objective-C protocols and categories. An interface/helper/protocol/category can contain only methods and properties Error: REINTRODUCE cannot be used in objects reintroduce is not supported for objects, Objective-C classes and Objective-C protocols. Error: Each argument must have its own location If locations for arguments