Question

我有以下课程

#import <UIKit/UIKit.h>

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

在function1中创建UIImageViewInfo时（下面的帖子）我得到了正确的结果

“UIImageViewInfo：0x1d8acd60; baseClass = UIImageView; frame =（0 0; 20 20）; opaque = NO; userInteractionEnabled = NO; tag = 2000; layer = CALayer：0x1d8a0560＆gt;＆gt;“

但是在function2中创建了一些东西（在下面发布）我得到 - （null）

UIImageViewInfo：0x8372c40; baseClass = UIImageView; frame =（0 0; 20 20）; alpha = 0; hidden = YES; opaque = NO; userInteractionEnabled = 没有; tag = 2000; layer = CALayer：0x8380090＆gt;＆gt; - （null）

为什么有 - （null）??

提前完成

P.S＆GT;这里有更多来自我的代码

-(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

没关系。它来自UIView的description方法，它相当复杂并且会转储有关视图的大量信息。其中一个条件是您的配置被绊倒并最终导致(null)。

安全无视。

~~UIKit中没有UIImageViewInfo类，因此实现必须在您的项目中。在该实现中，可能有description方法实现如下：~~

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

只有你的description可能更复杂，因为有时候这会输出。

~~当你对UIKit进行子类化时，不应该为UI的前缀添加前缀。~~

Answer 2

这是因为你的NSLog调用（你没有显示）要求第二个对象，而第二个对象是null。

为什么 - （null）在我的对象的末尾

2 个答案: