Objective c drawRect查看空数组

drawtestViewController.m中的按钮链接到ChalkBoard.m中的按钮操作。它用CGpoint对象填充pointArray。除了从drawRect查看外，此数组到处都是对象。从drawRect看来，我不知何故引用了原始数组的空副本，但我找不到任何错误

我已经上传了整个项目在

---

drawtestViewController.m中的按钮操作

- (IBAction)myDo {
   NSLog(@"-Button was pressed");    
  [self.board pushPoint:CGPointMake(100, 100 )];
  [self.board pushPoint:CGPointMake(10, 100 )];
  [self.graphicView setNeedsDisplay];
}

---

---

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将

drawRect

方法中的

pointArray

替换为

self.pointArray

。 使用

pointArray

时，变量按原样使用（不调用getter方法）。使用

self.pointArray

时，将使用getter方法

---

我还建议您将getter和setter留给编译器在init方法中生成和初始化pointArray。

问题实际上不在

黑板类中，而是在
drawtestViewcontroller中。您的
myDo
操作将点添加到
self.board
，但会将
setNeedsDisplay
消息发送到
self.graphicsview
，后者也是
黑板，但与您添加点的黑板不同

因此，您看到的第二条日志消息实际上来自一个完全不同的对象。
添加了self，但没有更改-（void）drawRect:（CGRect）rect{NSLog（@）-drawRect已执行，大小为%u，数组：%@，[self.pointArray count]，self.pointArray）；}只是为了让您高兴，你的回答让我在看了10小时我的观点后省去了麻烦：）祝你周末愉快！可能是你无意中有两个不同的黑板对象吗？一个在窗口中以便绘制，另一个连接到
板
插座，从而将点推送到它。尝试在两种方法中使用“%p”记录
self
。我找不到类似的内容：（我已将整个项目上载到
//  ChalkBoard.h
#import <UIKit/UIKit.h>

@interface ChalkBoard : UIView
-(void)pushPoint:(CGPoint)point;
@property (nonatomic,retain) NSMutableArray *pointArray;
@end

//ChalkBoard.m
#import "ChalkBoard.h"

@implementation ChalkBoard
@synthesize pointArray;

- (id)initWithFrame:(CGRect)frame
{
self = [super initWithFrame:frame];
    if (self) {
        self.backgroundColor = [UIColor blackColor];
    }
    return self;
}

-(NSMutableArray *)pointArray 
{
    if(pointArray == nil) pointArray = [[NSMutableArray alloc]initWithCapacity:10];
    return pointArray;
}

-(void)pushPoint:(CGPoint)point{
    // this is called from drawtestViewController.m by button press
    // in here the array is full and growing by each button press
    [self.pointArray addObject:[NSValue valueWithCGPoint:point]];
   NSLog(@"-pushPoint executed, size is %u, array: %@",[self.pointArray count], pointArray);
}

- (void)drawRect:(CGRect)rect{
// here array is always empty
NSLog(@"-DrawRect executed, size is %u, array: %@",[pointArray count], pointArray);
    if ([pointArray count] >1){   
       ... some irrelevant code
    }
}

@end

NSLog output

2012-04-09 11:34:39.145 drawtest[5260:f803] -DrawRect executed, size is 0, array: (null)
2012-04-09 11:34:41.261 drawtest[5260:f803] -Button was pressed
2012-04-09 11:34:41.262 drawtest[5260:f803] -pushPoint executed, size is 1, array: (
    "NSPoint: {100, 100}"
)
2012-04-09 11:34:41.264 drawtest[5260:f803] -pushPoint executed, size is 2, array: (
    "NSPoint: {100, 100}",
    "NSPoint: {10, 100}"
)
2012-04-09 11:34:41.266 drawtest[5260:f803] -DrawRect executed, size is 0, array: (null)
2012-04-09 11:34:42.825 drawtest[5260:f803] -Button was pressed
2012-04-09 11:34:42.826 drawtest[5260:f803] -pushPoint executed, size is 3, array: (
    "NSPoint: {100, 100}",
    "NSPoint: {10, 100}",
    "NSPoint: {100, 100}"
)
2012-04-09 11:34:42.827 drawtest[5260:f803] -pushPoint executed, size is 4, array: (
    "NSPoint: {100, 100}",
    "NSPoint: {10, 100}",
    "NSPoint: {100, 100}",
    "NSPoint: {10, 100}"
)
2012-04-09 11:34:42.829 drawtest[5260:f803] -DrawRect executed, size is 0, array: (null)