Objective-C Setter方法不起作用（簡單）

我不能爲了我的生活找出爲什麼myRect.origin.x和myRect.origin.y顯示的值爲0.對於廣泛的代碼的道歉，我做了刪除有些事情顯然不相關，但在其他事情上並不確定。另外，我知道我的相交方法還沒有正常工作，但我正在處理它。Objective-C Setter方法不起作用（簡單）

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

@class XYPoint; 

@interface Rectangle: GraphicObject 

@property float height, width; 

-(XYPoint*) origin; 
-(void) setOrigin: (XYPoint*) pt; 
-(float) area; 
-(float) perimeter; 
-(void) setHeight: (float) h andWidth: (float) w; 
-(void) translate: (XYPoint*) t; 
-(BOOL) containspoint: (XYPoint*) aPoint; 
-(Rectangle*) intersect: (Rectangle*) intr; 

@end 

@interface XYPoint: NSObject 

@property float x,y; 

-(void) setX:(float) xVal andY:(float) yVal; 

@end 


//Rectangle.m 

#import "Rectangle.h" 

@implementation Rectangle 

{ 
    XYPoint *origin; 
} 

@synthesize width, height; 

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

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

-(void) setHeight:(float) h andWidth: (float) w 
{ 
    width = w; 
    height = h; 
} 

-(void) setOrigin:(XYPoint *)pt 
{ 
    origin = pt; 
} 

-(XYPoint*) origin 
{ 
    return origin; 
} 

-(void) translate:(XYPoint *)t 
{ 
    origin = t; 
} 

-(BOOL) containspoint:(XYPoint *)aPoint 
{ 
    if (aPoint.x >= self.origin.x && aPoint.x <= self.origin.x + self.width && aPoint.y >= self.origin.y && aPoint.y <= self.origin.y + self.height) { 
     return YES; 
    } 
     else return NO; 

} 

-(Rectangle*) intersect: (Rectangle*) intr 

{ 

    Rectangle *zerorec = [[Rectangle alloc]init]; 
    Rectangle *rec1 = [[Rectangle alloc]init]; 
    Rectangle *rec2 = [[Rectangle alloc]init]; 

    zerorec.origin.x = 0; 
    zerorec.origin.y = 0; 
    zerorec.height = 0; 
    zerorec.width = 0; 

    if ((self.origin.x >= intr.origin.x && self.origin.x <= intr.origin.x + intr.width) || (intr.origin.x >= self.origin.x && intr.origin.x >= self.origin.x + self.width)) 
    { 
     if ((self.origin.y >= intr.origin.y && self.origin.y <= intr.origin.y + intr.height) || (intr.origin.y >= self.origin.y && intr.origin.y >= self.origin.y + self.height)) 

      NSLog(@"The rectangles intersect"); 
      //rec 1 = the rectangle with the greater x value 

      if (self.origin.x >= intr.origin.x && self.origin.x <= intr.origin.x + intr.width) 
       rec1 = self, rec1.origin = self.origin, rec2 = intr, rec2.origin = intr.origin; 

      else rec2 = self, rec2.origin = self.origin, rec1 = intr, rec1.origin = intr.origin; 



      Rectangle *returnedRec = [[Rectangle alloc]init]; 

      returnedRec.origin.x = rec1.origin.x; 
      returnedRec.origin.y = rec2.origin.y; 

      //rec 1 = rectangle with greater y value 

      if (self.origin.y > intr.origin.y) 
       rec1 = self, rec2 = intr; 
      else rec1 = intr, rec2 = self; 

      returnedRec.height = rec1.height - (rec1.origin.y - rec2.origin.y); 
      returnedRec.width = rec1.width - (rec2.origin.y - rec1.origin.y); 

      return returnedRec; 
    } 



     else return zerorec; 

    } 

@end 


@implementation XYPoint 

@synthesize x, y; 

-(void) setX:(float) xVal andY:(float) yVal 

{ 
    x = xVal; 
    y = yVal; 
} 

@end 

//main.m 

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

int main(int argc, const char * argv[]) 
{ 

    @autoreleasepool { 

     Rectangle *returnedRect = [[Rectangle alloc]init]; 

     Rectangle *myRect = [[Rectangle alloc]init]; 
     Rectangle *yourRect = [[Rectangle alloc]init]; 

     [myRect.origin setX:3 andY: 2]; 
     [myRect setHeight:4 andWidth:5]; 
     [yourRect.origin setX:6 andY:4]; 
     [yourRect setHeight:7 andWidth:9]; 

     myRect.origin.x = 2; 
     myRect.origin.y = 3; 

     returnedRect = [myRect intersect:yourRect]; 

     NSLog(@"x = %f, y = %f", returnedRect.origin.x, returnedRect.origin.y); 

     NSLog(@"height = %f, width = %f", returnedRect.height, returnedRect.width); 

     NSLog(@"%f, %f", myRect.origin.x, myRect.origin.y); 


    } 
    return 0; 
}

正如你所看到的，我嘗試使用setX的方法和Y與設置x和y的值明確，程序仍返回x和myRect.origin的y值的值爲0一起。

來源

2013-07-25 Ronald

您的來源永遠是零，因爲您永遠不會創建XYPoint的對象。添加到您的Rectangle類：

- (id)init 
{ 
    self = [super init]; 
    if (self) { 
     origin = [[XYPoint alloc] init]; 
    } 
    return self; 
}

來源

2013-07-25 06:55:09 shadowhorst

謝謝，本書中的這個問題來自於（我錯過了這一部分）增加了類似於你的答案的東西，但是在SetOrigin方法實現本身中，因爲我們還沒有作爲一種方法被初始化。我不明白的（以及我現在所理解的，下面的內容可能並不準確）是，作爲Rectangle類的一部分的原點只爲原點分配空間但不初始化它，因爲它是一個對象本身，它需要在可以使用之前進行初始化。 – Ronald

不完全是，當您調用類本身的alloc方法時，您的XYPoint的內存會被分配。通過將原點添加到您的Rectangle類中，您只需添加一個指向XYPoint對象的指針即可。 – shadowhorst

看起來你從來沒有創建XYPoint所以你發送的消息數量來nil一個實例。

你應該使用CGRect（即使你的類是它的包裝），因爲它會讓你的代碼和生活變得更簡單。

來源

2013-07-25 06:56:36 Wain

Objective-C Setter方法不起作用（簡單）

回答

相關問題