Will的部落格

若用繼承擴充原本既有的程式碼，

可相對節省不少時間在重新打造輪子上，

本範例先創造一個矩形Rectangle class，

在創造一個Square class並繼承於Rectangle，

並重複利用area, perimeter這兩個method

最後用main.m黨印出並驗證，程式碼如下，

Rectangle.h

#import <Foundation/Foundation.h>

@interface Rectangle : NSObject

@property int width, height;

-(int) area;
-(int) perimeter;
-(void) setWidth: (int) w andHeight: (int) h;

@end

Rectangle.m

#import "Rectangle.h"

@implementation Rectangle

@synthesize width, height;

-(void) setWidth: (int) w andHeight: (int) h
{
    width = w;
    height = h;
}

-(int) area
{
    return width * height;
}

-(int) perimeter
{
    return (width + height) * 2;
}

@end

Square.h

#import "Rectangle.h"

@interface Square : Rectangle //繼承於Rectangle

-(void) setSide: (int) s;
-(int) side;

@end

Square.m

#import "Square.h"

@implementation Square

-(void) setSide: (int) s
{
    [self setWidth: s andHeight: s];
}

-(int) side
{
    return self.width;
}

@end

main.m

#import <Foundation/Foundation.h>
#import "Rectangle.h"
#import "Square.h"

int main(int argc, const char * argv[])
{
    @autoreleasepool
    {
        Rectangle * rectangle = [[Rectangle alloc]init];
        [rectangle setWidth:6 andHeight:10];
        
        NSLog(@"rectangle: w = %i, h = %i", rectangle.width, rectangle.height);
        NSLog(@"Area = %i, Perimeter = %i", [rectangle area], [rectangle perimeter]);
        

        Square * square = [[Square alloc]init];
        [square setSide: 8];
        
        NSLog(@"square: s = %i,", square.side);
        NSLog(@"Area = %i, Perimeter = %i", [rectangle area], [rectangle perimeter]); 
       //透過繼承, 由此可見不用在Square.m重新實作area與perimeter這兩個method
        
    }
    return 0;
}