JSON解析向iOS返回null（json字符串看起来正确）

Question

我正在尝试将JSON转换为iOS应用，但始终获取NULL值。

 - (id)initWithDictionary:(NSDictionary *)dictionary { self.name = [dictionary valueForKey:@"name"]; self.amount = [NSString stringWithFormat:@"%@", [dictionary valueForKey:@"amount"]]; self.goalId = [dictionary valueForKey:@"id"]; self.createdAt = [dictionary valueForKey:@"created_at"]; self.updatedAt = [dictionary valueForKey:@"updated_at"]; return self; } + (NSArray *)findAllRemote { NSURL *url = [NSURL URLWithString:@"http://localhost:3000/goals.json"]; NSError *error = nil; NSString *jsonString = [NSString stringWithContentsOfURL:url encoding:NSUTF8StringEncoding error:&error]; NSLog(@"my string = %@", jsonString); NSMutableArray *goals = [NSMutableArray array]; if (jsonString) { SBJSON *json = [[SBJSON alloc] init]; NSArray *results = [json objectWithString:jsonString error:&error]; [json release]; for (NSDictionary *dictionary in results) { Goal *goal = [[Goal alloc] initWithDictionary:dictionary]; [goals addObject:goal]; [goal release]; } } return goals; } 

JSON字符串看起来正确：

我的字符串= [{“目标”：{“数量”：“ 100.0”，“ created_at”：“ 2011-08-20T00：55：34Z”，“ id”：1，“名称”：“用户”，“ updated_at “：” 2011-08-20T00：55：34Z“}}，{”目标“：{”金额“：” 200.0“，” created_at“：” 2011-08-20T00：56：48Z“，” id“： 2，“名称”：“ User2”，“ updated_at”：“ 2011-08-20T00：56：48Z”}}，{“目标”：{“金额”：“ 19999.0”，“ created_at”：“ 2011-08 -20T19：15：10Z“，” id“：3，”名称“：”这是我的目标“，” updated_at“：” 2011-08-20T19：15：10Z“}}，{”目标“：{”数量“：” 0.0“，” created_at“：” 2011-08-20T20：46：44Z“，” id“：4，”名称“：”目标“，” updated_at“：” 2011-08-20T20：46： 44Z“}}]

我想念一些基本的东西。

更新 ：

这是一行返回NULL（从另一个类）的行：

- (IBAction)refresh {
[UIApplication sharedApplication].networkActivityIndicatorVisible = YES;
self.goals = [Goal findAllRemote];
[self.tableView reloadData];
[UIApplication sharedApplication].networkActivityIndicatorVisible = NO;
}

- (void)viewDidLoad
{
[super viewDidLoad];

self.title = @"Goals";
self.navigationItem.leftBarButtonItem = self.editButtonItem;

UIBarButtonItem *refreshButton = [[UIBarButtonItem alloc] 
                                      initWithBarButtonSystemItem:UIBarButtonSystemItemRefresh
                                  target:self 
                                  action:@selector(refresh)];
self.navigationItem.rightBarButtonItem = refreshButton;
[refreshButton release];

[self refresh];

}


 - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{


static NSString *CellIdentifier = @"GoalCellId";

UITableViewCell *cell = 
[tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil) {
    cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleValue1
                                   reuseIdentifier:CellIdentifier] autorelease];
}

Goal *goal = [goals objectAtIndex:indexPath.row];

cell.textLabel.text = goal.name;
cell.detailTextLabel.text = goal.amount;

return cell;
}

目标名称和目标金额为空。

Answer 1

这可能不是问题的一部分，但您应该调用[self init] （或更重要的是，通过继承调用[super init] ）：

- (id)initWithDictionary:(NSDictionary *)dictionary {
    if (self = [self init]) {
      self.name      = [dictionary valueForKey:@"name"];
      self.amount    = [NSString stringWithFormat:@"%@", 
                      [dictionary valueForKey:@"amount"]];
      self.goalId    = [dictionary valueForKey:@"id"];
      self.createdAt = [dictionary valueForKey:@"created_at"];
      self.updatedAt = [dictionary valueForKey:@"updated_at"];
    }
    return self;
}

也：

    for (NSDictionary *dictionary in results) {
       Goal *goal = [[Goal alloc] initWithDictionary:
          [dictionary objectForKey:@"goal"]];
       [goals addObject:goal];
       [goal release];
    }

密钥更改是第3行中的[dictionary objectForKey:@"goal"] 。

JSON数组由具有单个goal成员的对象组成，具有initWithDictionary方法要查找的属性。