类的使用与继承

//长方形的类的声明与实现
#import <Foundation/Foundation.h>

@interface Rect2 : NSObject
{
//    float chang;
//    float w;
}
@property float chang;
@property float w;

- (float)sizeOfRect;
@end


#import "Rect2.h"

@implementation Rect2
//@synthesize chang;
//@synthesize w;

- (float)sizeOfRect
{
    NSLog(@"%@", self);
    return  (self.chang)*(self.w);
}
@end

//长方体的类的声明与定义
#import <Foundation/Foundation.h>
#import "Rect2.h"
@interface LiFangTi : Rect2
{
//    float height;
}
@property float height;
- (float)tiJiFor;
@end


#import "LiFangTi.h"

@implementation LiFangTi
-(float)tiJiFor
{
    return self.w*self.height*self.chang;
}
@end



#import "ViewController.h"
#import "LiFangTi.h"
#import "Rect2.h"
@interface ViewController ()
            

@end

@implementation ViewController
            
- (void)viewDidLoad {
    [super viewDidLoad];
    Rect2 *rect=[[Rect2 alloc]init];
    rect.chang=1;
    rect.w    =2;
    NSLog(@"%@", rect);
    NSLog(@"%f",[rect sizeOfRect]);
    
    LiFangTi *liFangTi=[[LiFangTi alloc]init];
    liFangTi.chang=1.0;
    liFangTi.w    =3.0;
    liFangTi.height=3.0;
    NSLog(@"%f",[liFangTi tiJiFor]);
}