我對我所理解的Objective-C中指針和引用的使用方式的基本錯誤。我一直在尋找這個問題，調整我的代碼等等，但都無濟於事。Objective-C中的基本指針/引用問題 - 一個實例中的訪問器方法影響所有類級別的實例
我知道我在做一個簡單的錯誤的地方（新手的Objective-C，而不是OOP）只是我沒有看到它......哎呀：P
我歡迎任何和所有輸入從你們自己的更聰明的角度來看。 :)
如果我可以說明我的問題，它是這樣的：
在我「的main.m」文件我實例化一個特定的「矩形」類的4種獨立的情況下，每一個獨特的尺寸和笛卡爾座標可以通過getter（s）/ setter（s）訪問。 合成「寬度」和「高度」屬性，而座標包裝在可通過自定義方法訪問的對象（XYPpoint類）內。
當我訪問寬度和高度屬性時，我能夠爲任何和所有實例獲取/設置唯一值，但是當我嘗試使用座標時，我不可避免地最終會同時更改所有實例的所有實例。
我在做什麼錯？我可以看到，我的起源對象僅實例化了1個（而不是4個），但我不明白爲什麼？！？
* * *編輯： 按hamstergene的友好建議（見1日回答）我又試了一次，得到它通過聲明*原點爲@property工作。不過，我還必須首先@synthesize它，然後在@implementation中覆蓋它。我不知道爲什麼，但這似乎有點像矯枉過正。這是正確的方式嗎？此外Xcode中似乎不喜歡它，並拋出一個警報（編譯仍然雖然）
至於這裏的代碼是（短）：
========== ================================================== ======================
（接口，用於包裝類的座標的對象）
// XYPoint.h
//
#import <Foundation/Foundation.h>
@interface XYPoint : NSObject
@property float x, y;
-(void) setX: (float) xVal andY: (float) yVal;
@end
======= ================================================== ====================== ===
（實施包裝類的座標的對象）
// XYPoint.m
//
#import "XYPoint.h"
@implementation XYPoint
@synthesize x, y;
-(void) setX: (float) xVal andY: (float) yVal {
x = xVal;
y = yVal;
}
@end
========================== ================================================== ======
（接口爲我的Rectangle類）
// Rectangle.h
//
#import <Foundation/Foundation.h>
#import "XYPoint.h"
@interface Rectangle : NSObject
@property float width,
height;
-(XYPoint *) origin;
-(void) setWidth: (float) w andHeight: (float) h;
-(void) setOrigin: (XYPoint *) pt;
-(void) printData;
@end
========================== ================================================== ======
（實施我的Rectangle類）
// Rectangle.m
//
#import "Rectangle.h"
@implementation Rectangle
@synthesize width, height;
XYPoint *origin;
-(void) setWidth:(float) w andHeight: (float) h {
width = w;
height = h;
}
-(XYPoint *) origin {
return origin;
}
-(void) setOrigin: (XYPoint *) pt {
if (! origin) {
NSLog(@"origin object created");
origin = [ [ XYPoint alloc ] init ];
}
origin.x = pt.x;
origin.y = pt.y;
}
-(void) printData {
NSLog(@"origin coordinates (%.1f, %.1f)", origin.x, origin.y);
NSLog(@"Width = %.1f, Height = %.1f\n");
}
@end
================================== ================================================
（和最後的main.m）
// main.m
//
#import "Rectangle.h"
int main(int argc, const char * argv[]) {
@autoreleasepool {
XYPoint *rect1Origin = [ [ XYPoint alloc ] init ];
XYPoint *rect2Origin = [ [ XYPoint alloc ] init ];
XYPoint *rect3Origin = [ [ XYPoint alloc ] init ];
XYPoint *rect4Origin = [ [ XYPoint alloc ] init ];
Rectangle *rect1 = [ [ Rectangle alloc ] init ];
Rectangle *rect2 = [ [ Rectangle alloc ] init ];
Rectangle *rect3 = [ [ Rectangle alloc ] init ];
Rectangle *rect4 = [ [ Rectangle alloc ] init ];
[ rect1Origin setX: 200 andY: 420 ];
[ rect1 setOrigin: rect1Origin ];
[ rect1 setWidth: 250 andHeight: 75 ];
NSLog(@"1st Rectangle\n------------------------------------------");
[ rect1 printData ];
[ rect2Origin setX: 400 andY: 300 ];
[ rect2 setOrigin: rect2Origin ];
[ rect2 setWidth: 100 andHeight: 180 ];
NSLog(@"2nd Rectangle\n------------------------------------------");
[ rect2 printData ];
[ rect3Origin setX: 99 andY: 99 ];
[ rect3 setOrigin: rect3Origin ];
[ rect3 setWidth: 50 andHeight: 450 ];
NSLog(@"3rd Rectangle\n------------------------------------------");
[ rect3 printData ];
[ rect4Origin setX: 20 andY: 100 ];
[ rect4 setOrigin: rect4Origin ];
[ rect4 setWidth: 10 andHeight: 3 ];
NSLog(@"4th Rectangle\n------------------------------------------");
[ rect4 printData ];
NSLog(@"\n------------------------------------------");
NSLog(@"1st Rectangle again...\n------------------------------------------");
[ rect1 printData ];
NSLog(@"2nd Rectangle again...\n------------------------------------------");
[ rect2 printData ];
NSLog(@"3rd Rectangle again...\n------------------------------------------");
[ rect3 printData ];
NSLog(@"4th Rectangle again...\n------------------------------------------");
[ rect4 printData ];
NSLog(@"\n\n********* All rects have the same coordinates why does this happen?");
}
return 0;
}
================================== ================================================
OUTPUT
origin object created
1st Rectangle
------------------------------------------
origin coordinates (200.0, 420.0)
Width = 250.0, Height = 75.0
2nd Rectangle
------------------------------------------
origin coordinates (400.0, 300.0)
Width = 100.0, Height = 180.0
3rd Rectangle
------------------------------------------
origin coordinates (99.0, 99.0)
Width = 50.0, Height = 450.0
4th Rectangle
------------------------------------------
origin coordinates (20.0, 100.0)
Width = 10.0, Height = 3.0
------------------------------------------
1st Rectangle again...
------------------------------------------
origin coordinates (20.0, 100.0)
Width = 250.0, Height = 75.0
2nd Rectangle again...
------------------------------------------
origin coordinates (20.0, 100.0)
Width = 100.0, Height = 180.0
3rd Rectangle again...
------------------------------------------
origin coordinates (20.0, 100.0)
Width = 50.0, Height = 450.0
4th Rectangle again...
------------------------------------------
origin coordinates (20.0, 100.0)
Width = 10.0, Height = 3.0
********* All rects have the same coordinates why does this happen?
爲了什麼它的價值，這些類（實際結構）已經存在於CoreGraphics。看看CGPoint和CGRect –
謝謝詹姆斯。構建這些類實際上是我正在閱讀的這本書的一部分（Steve Kochan的「Objective-C中的編程」）:) –