Objective C 子类重写超类中的方法

使用Objective C编程语言时，我们可以创建一个子类来继承一个超类。子类可以重写超类中的方法，以便根据自己的需求来定制功能。这种重写方法的能力使得我们能够更好地扩展和定制现有的代码，而无需修改超类本身。

objective-c
@interface SuperClass : NSObject
- (void)printMessage;
@end
@implementation SuperClass
- (void)printMessage {
    NSLog(@"This is the printMessage method from the SuperClass.");
}
@end
@interface SubClass : SuperClass
@end
@implementation SubClass
- (void)printMessage {
    NSLog(@"This is the printMessage method from the SubClass.");
}
@end

objective-c
@interface Shape : NSObject
- (void)calculateArea;
@end
@implementation Shape
- (void)calculateArea {
    NSLog(@"This is the calculateArea method from the Shape class.");
}
@end
@interface Rectangle : Shape
@end
@implementation Rectangle
- (void)calculateArea {
    NSLog(@"This is the calculateArea method from the Rectangle class.");
    CGFloat width = 5.0;
    CGFloat height = 10.0;
    CGFloat area = width * height;
    NSLog(@"The area of the rectangle is %f.", area);
}
@end

This is the calculateArea method from the Rectangle class.
The area of the rectangle is 50.000000.