Objective-C: Instance Variables

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