Objective-C: Instance Variables

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Reference: Encapsulating Data

  • Use properties (accessible from outside the class in question):
    @interface XYZPerson : NSObject
@property NSString *firstName;
@property NSString *lastName;
@end
    • These @property declarations also synthesize instance variables, so you can do this:
      - (void)someMethod {
    _firstName = @"Bob";
}
    • Use @synthesize to control the name of the generated instance variable:
      @implementation XYZPerson
@synthesize firstName = ivar_firstName;
@end
  • Or define instance variables directly:
    @implementation SomeClass {
    NSString *_anotherCustomInstanceVariable;
}
...
@end
    • Block scoping is relevant here; the following is incorrect and declares global variables instead (source):
      @implementation SomeClass 
NSString *_anotherCustomInstanceVariable;
    
...
@end
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