Objective-C Class

Class Declaration

Objective-C classes are declared using @interface block, and implementations are specified in @implementation block.

  // ---- @interface ----
  @interface Fraction : NSObject {  // inherit from NSObject
      int numerator;
      int denominator;
  }
  - (void)print;
  - (void)setNumerator:(int)n;
  - (void)setDenominator:(int)d;
  @end

  // ---- @implementation ----
  @implementation Fraction   // you can optionally specify :NSObject after Fraction
  - (void)print { NSLog(@"%i/%i", numerator, denominator); }
  - (void)setNumerator:(int)n { numerator = n; }
  - (void)setDenominator:(int)d { denominator = d; }
  @end

Properties

@property is a shortcut for declaring getter and setter methods on your class' instance variables. It is a feature only available in Objective-C 2.0. Not only are these synthesized getters and setters atomic i.e. thread-safe, the setter methods will also automatically release the overwritten objects.

More Resources

• Apple Doc the official documentation on properties.
• Cocoa with Love has more on the merit of property.
• Cocoacast a tutorial on property.
• Wikipeida Objective-C 2.0 Properties.