由于未捕获的异常“NSUnknownKeyException”而终止应用程序此类不符合键 .img 的键值编码

Question

尝试异步加载图像我收到此错误 “由于未捕获的异常 'NSUnknownKeyException' 导致应用程序终止，原因：'[valueForUndefinedKey:]：此类不符合键值编码关键img。'" 我的代码如下

 NSString *str = "URL of an image";

    NSMutableDictionary *record = [NSMutableDictionary dictionary];
    [record setObject:str forKey:@"img"];

    record = [_array objectAtIndex:indexPath.row];



   dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH,  0ul);
    if ([record valueForKey:@"img"]) {
        NSLog(@"in if");
        cell.m_img.image =  [record valueForKey:@"img"];
    } else {
        dispatch_async(queue, ^{
             NSLog(@"in else");
            NSURL  *imageurl = [[NSURL alloc] initWithString:str];
            NSData *image = [[NSData alloc] initWithContentsOfURL:imageurl];

            dispatch_async(dispatch_get_main_queue(), ^{
                [record setValue:[UIImage imageWithData:image] forKey:@"img"];

                [tableView reloadRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationNone];
            });
        });
    }

请告知我在哪里出错了。 谢谢 马尤尔

Answer 1

替换

[record valueForKey:@"img"]

与

[record objectForKey:@"img"]

Answer 2

 Check if object in array is of dictionary type

  NSString *str = "URL of an image";

    NSMutableDictionary *record = [NSMutableDictionary dictionary];

if([[_array objectAtIndex:indexPath.row]isKindOfClass:[NSDictionary class]])
    record = [_array objectAtIndex:indexPath.row];
else
      [record setObject:str forKey:@"img"];


   dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH,  0ul);
    if ([record valueForKey:@"img"]) {
        NSLog(@"in if");
        cell.m_img.image =  [record valueForKey:@"img"];
    } else {
        dispatch_async(queue, ^{
             NSLog(@"in else");
            NSURL  *imageurl = [[NSURL alloc] initWithString:str];
            NSData *image = [[NSData alloc] initWithContentsOfURL:imageurl];

            dispatch_async(dispatch_get_main_queue(), ^{
                [record setValue:[UIImage imageWithData:image] forKey:@"img"];

                [tableView reloadRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationNone];
            });
        });
    }

Answer 3

这条线很可能

[记录valueForKey:@"img"]

objectForKey: 将在未设置键 img 的情况下返回 nil。在您的情况下是更好的选择。

但是，请总体检查您的代码。您首先创建一个新的NSMutableDictionary 并将其分配给record。然后将一个字符串对象添加到该字典中。到目前为止还好。 之后，您也从分配给 record 的数组 _array 中获取一个对象。到那时，您不再对新创建的字典有任何引用。是不是故意的。如果您不使用 ARC，那么您会在此处创建内存泄漏。

编辑以回应以下评论：

NSMutableDictionary *record = [NSMutableDictionary dictionary]; // here you create a new empty instance of NSMutableDictionary and store it in record. It has a retain count of 1
[record setObject:str forKey:@"img"]; // here you add an object to that new dictionary. Now it has exactly one entry with the key "img"
record = [_array objectAtIndex:indexPath.row]; //and here you discard the retained newly creaded dictionary by assigning another one from the array _array. What is the purpose of that?

Answer 4

在您的 cmets 和答案的帮助下解决了问题。我所做的是在 Globally used 类中创建 NSMutable Dictionary 并初始化变量。谢谢大家的帮助

arr = [[NSMutableDictionary alloc] init];


dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH,  0ul);
    if ([[[DataManager sharedInstance] arr] objectForKey:str]) {
        NSLog(@"in if");

         [cell m_img].image = [UIImage imageWithData:[[[DataManager sharedInstance] arr] objectForKey:str]]; 
    } else {
        dispatch_async(queue, ^{
             NSLog(@"in else");



                NSURL  *imageurl = [[NSURL alloc] initWithString:str];
                NSData *image = [[NSData alloc] initWithContentsOfURL:imageurl];
                [[[DataManager sharedInstance] arr] setObject :image forKey:str];
                [cell m_img].image = [UIImage imageWithData:[[[DataManager sharedInstance] arr] objectForKey:str]]; 

        });
    }