爲什麼 - （空）在我的對象

Question

結束時，我有下面的類

#import <UIKit/UIKit.h> 

@interface UIImageViewInfo : UIImageView 
@property(nonatomic,strong) NSString* colorInfo; 
@end 

在功能1（後下）創建UIImageViewInfo當我得到正確的結果

「UIImageViewInfo ：0x1d8acd60;基類=的UIImageView;幀=（0 0; 20 20）;不透明= NO; userInteractionEnabled = NO;標記= 2000;層= 的CALayer：0x1d8a0560 >>」

但創造的函數2東西（貼在下面），我得到的 - （空）

UIImageViewInfo：0x8372c40; baseClass = UIImageView; frame =（0 0; 20 20）; alpha = 0;隱藏= YES; opaque = NO; userInteractionEnabled = 否; tag = 2000; layer = CALayer：0x8380090 >> - （null）

爲什麼會有 - （null）？

Thanx提前

PS>這裏是我的代碼

-(void)function1{ 
UIImageViewInfo *image; 
self.solutionPinSlots = [[NSMutableArray alloc] init]; 

for (int i=0; i<M; i++) { 
    image = [[UIImageViewInfo alloc] initWithImage:[UIImage imageNamed:@"solutionPeg@2x.png"]]; 
    image.translatesAutoresizingMaskIntoConstraints=NO; 

    image.hidden=YES; 
    image.alpha = 0; 
    image.colorInfo = @"clear"; 

    image.tag = 2000*(self.brainController.slotsIndex+1) +i; 
    [self.solutionPinSlots addObject:image]; 
    [self.view addSubview:(UIImageViewInfo *)self.solutionPinSlots[i]]; 
} 
NSLog(@"solutionSlots: %@",self.solutionPinSlots); 
__block int counter = 0; 
[self.brainController.solution enumerateObjectsUsingBlock:^(NSString *peg, NSUInteger idx, BOOL *stop){ 

    for (int i=0;i<M;i++) { 
     if ([self.brainController.slots[self.brainController.slotsIndex][i] isEqual:peg]) { 

      if (i==idx) { 
      ((UIImageViewInfo *) self.solutionPinSlots[counter]).backgroundColor = [UIColor whiteColor]; 
       ((UIImageViewInfo *) self.solutionPinSlots[counter]).colorInfo=@"white"; 
      }else{ 
       ((UIImageViewInfo *) self.solutionPinSlots[counter]).backgroundColor = [UIColor blackColor]; 
       ((UIImageViewInfo *) self.solutionPinSlots[counter]).colorInfo=@"black";} 
      ((UIImageViewInfo *) self.solutionPinSlots[counter]).hidden=NO; 
      ((UIImageViewInfo *) self.solutionPinSlots[counter++]).alpha=1; 
     } 
    } 

}]; 

[self.solutionPinSlots shuffle]; 

[self updateSolutionPinSlots]; 

}

-(void)function2{ 
NSString *obj; 


for (int idx=0; idx< M;idx++) { 
    UIImageViewInfo *image = [[UIImageViewInfo alloc] initWithImage:[UIImage imageNamed:@"solutionPeg@2x.png"]]; 
    image.translatesAutoresizingMaskIntoConstraints=NO; 
    obj = (NSString *) [self.solutionPinSlots objectAtIndex:idx]; 
    image.tag=2000*(self.brainController.slotsIndex+1)+idx; 
    image.hidden=NO; 
    image.alpha = 1; 
    if ([obj isEqualToString:@"clear"]) { 
     image.hidden=YES; 
     image.alpha = 0; 
     image.colorInfo=@"clear"; 
     image.backgroundColor=[UIColor clearColor]; 
    }else if ([obj isEqualToString:@"white"]){ 
     image.colorInfo=@"white"; 
     image.backgroundColor=[UIColor whiteColor]; 
    }else if ([obj isEqualToString:@"black"]){ 
     image.colorInfo=@"black"; 
     image.backgroundColor=[UIColor blackColor]; 
    }else{ 
     NSLog(@"Something is Wrong!!!"); 
    } 

    [self.solutionPinSlots replaceObjectAtIndex:idx withObject:image]; 

    [self.view addSubview:image]; 
} 

}

Answer 1

更因爲你的NSLog調用（你不這樣做顯示）是要求第二個對象，第二個對象是空的。

Answer 2

沒關係。它來自UIView的description方法，這是相當複雜的，並轉儲了一堆關於視圖的信息。其中一個條件被您的配置絆倒，導致(null)結束。

安全無視。

UIKit中沒有 UIImageViewInfo類，所以實現必須在您的項目中。在此實施，有可能是一個 description方法來實現這樣的：

- (NSString*)description { 
    .... 
    return [NSString stringWithFormat:@"UIImageViewInfo:%p; %@ - %@", self, [super description], someInstanceVariableThatHappensToBeNil]]; 
} 

只有你description可能更復雜，因爲有時有時做這一點，輸出。

當子類化UIKit時，不應該在 UI前綴類。