使用返回的 JSON 在表视图单元格中填充 UILabel

Question

我正在尝试将 JSON 数据从字段"field_message_subject"和"field_message_body"拉到我的应用程序中的表格单元格。我使用以下代码执行此操作，并且成功返回数据，但我的应用程序崩溃并且未填充标签。崩溃错误是：

由于未捕获的异常"NSRangeException"而终止应用程序，原因： '*** -[__NSArrayM 对象索引：]： 索引 1 超出边界 [0 .. 0]'

Viewcontroller.m

    - (void)viewDidLoad {
        [super viewDidLoad];

        NSDictionary *entityData = [NSDictionary dictionaryWithObject:[NSString stringWithFormat:@"1"] forKey:@"uid"];
        [DIOSEntity
         entityGet:entityData
         name:@"entity_message"
         eid:@"uid"
         success:^(AFHTTPRequestOperation *op, id response) {
             self.messages = [NSMutableArray arrayWithObject:(NSDictionary*)response];
             dispatch_async(dispatch_get_main_queue(), ^(void){
                  [self.tableView reloadData];
             });
         }
         failure:^(AFHTTPRequestOperation *op, NSError *err) { NSLog(@"failed to get data"); }
         ];
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{

    static NSString *PointsTableIdentifier = @"MyMessagesCell";
    MyMessagesCell *cell = (MyMessagesCell *)[tableView dequeueReusableCellWithIdentifier:PointsTableIdentifier];
    if (cell == nil)
    {
        NSArray *nib = [[NSBundle mainBundle] loadNibNamed:@"MyMessagesCell" owner:self options:nil];
        cell = [nib objectAtIndex:0];
    }
    NSDictionary *receivedSubjectLine = [self.messages objectAtIndex:indexPath.row];
   [[cell subjectLine] setText:[receivedSubjectLine objectForKey:@"field_message_subject"]];
    NSLog(@"Received message subject is here %@", receivedSubjectLine);
 return cell;
}

请参阅下面返回的 JSON 格式：

 2016-02-02 10:37:19.996 app[4208:1406692] Messages are as follows (
            {
            arguments =         (
            );
            data =         (
            );
            "field_message_body" =         {
                und =             (
                                    {
                        format = "<null>";
                        "safe_value" = "Testing message center";
                        value = "Testing message center";
                    }
                );
            };
            "field_message_group_ref" =         (
            );
            "field_message_subject" =         {
                und =             (
                                    {
                        format = "<null>";
                        "safe_value" = Testing;
                        value = Testing;
                    }
                );
            };
            "field_message_user_ref" =         (
            );
            language = en;
            mid = 1;
            "rdf_mapping" =         (
            );
            timestamp = 1447260780;
            type = "private_message";
            uid = 1;
        }
    )

Answer 1

根据您的 JSON 格式，访问field_message_subject应该是这样的

 [[[[receivedSubjectLine objectForKey:@"field_message_subject"] objectForKey:@"und"] objectAtIndex:0] objectForKey:@"value"];

Answer 2

表视图应该知道它需要多少个单元格。定义此表视图数据源方法以设置所需的行数。

-(NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
    return [self.messages count];
}

顺便说一下，如果你增加行数，你应该在viewDidLoad初始化你的self.messages，并添加带有h addObject:的条目;

self.messages = [NSMutableArray arrayWithObject:(NSDictionary*)response];

因为这将始终

为您的数组分配新空间，并且其大小将始终为 1。

编辑

    NSDictionary *receivedSubjectLine = [self.messages objectAtIndex:indexPath.row];
   NSArray * val = receivedSubjectLine[@"und"];
   NSString *textToWrite = val[0][@"value"];
       [cell.subjectLine setText:textToWrite];

在字段中写入文本value

Answer 3

您正在将response（NSDictionary）添加到self.messages。代码中没有其他任何地方插入到self.messages 中。因此messages数组将始终保存一个值。您正在尝试从数组中获取行索引处messages对象。因此，如果行数大于 1，您的应用程序将崩溃，因为messages只包含 1 个对象。