Objective-C Language Properties Custom getters and setters
Example
The default property getters and setters can be overridden:
@interface TestClass
@property NSString *someString;
@end
@implementation TestClass
// override the setter to print a message
- (void)setSomeString:(NSString *)newString {
NSLog(@"Setting someString to %@", newString);
// Make sure to access the ivar (default is the property name with a _
// at the beginning) because calling self.someString would call the same
// method again leading to an infinite recursion
_someString = newString;
}
- (void)doSomething {
// The next line will call the setSomeString: method
self.someString = @"Test";
}
@end
This can be useful to provide, for example, lazy initialization (by overriding the getter to set the initial value if it has not yet been set):
- (NSString *)someString {
if (_someString == nil) {
_someString = [self getInitialValueForSomeString];
}
return _someString;
}
You can also make a property that computes its value in the getter:
@interface Circle : NSObject
@property CGPoint origin;
@property CGFloat radius;
@property (readonly) CGFloat area;
@end
@implementation Circle
- (CGFloat)area {
return M_PI * pow(self.radius, 2);
}
@end
