ios - 实例变量总是返回零

Question

我有一个实例变量数组:

       @interface ChannelsVC ()
        {
        NSArray *arrayofFrequencies;
        }
    }
    @end

@implementation ChannelsVC
......

在“viewDidLoad”中进行分配

arrayofFrequencies=[[NSArray alloc]init];

然后，我从 JSON 数据源向数组中插入数据:

-(void)GetFrequencies{

    NSString *urla=@"http://xxxxxxxx";
    NSString *uria = [urla stringByAppendingString:self.lien_satellite];
    NSURL *urlFrequencies= [ NSURL URLWithString:uria];

    NSLog(@"Frequencies URI: %@",uria); //correct URI



    NSURLRequest *request = [NSURLRequest requestWithURL:urlFrequencies];

    AFJSONRequestOperation *operation = [AFJSONRequestOperation JSONRequestOperationWithRequest:request success:^(NSURLRequest *request, NSHTTPURLResponse *response, id JSON) {
        arrayofFrequencies=[JSON valueForKeyPath:@"frequency"];

        NSLog(@"Frequencies count: %lu", (unsigned long)[arrayofFrequencies count]);//the count here is correct, I have data in the array

     } failure:nil];

    [operation start];

 }

问题是，当想要创建一个 UITableView，其部分数为“[arrayofFrequencies count];”时，它总是返回“0”!它是一个实例变量，它在“GetFrequencies”函数之外返回零。

- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
    NSLog(@"number of sections %ld",(long)[arrayofFrequencies count]); // always returns 0
    return [arrayofFrequencies count];
}

我做错了什么吗？

感谢您的帮助。

控制台输出:

013-06-25 12:58:00.163 Frequencies[840:c07] number of sections 0
2013-06-25 12:58:00.165 Frequencies[840:c07] number of sections 0
2013-06-25 12:58:00.641 Frequencies[840:c07] Frequencies count: 4

Answer 1

之后调用[tableView reloadData]

NSLog(@"Frequencies count: %lu", (unsigned long)[arrayofFrequencies count]);//the count here is correct, I have data in the array

要理解的一点是在 viewDidLoad 中调用 tableView 委托(delegate)。那时数组计数为零。后来数组充满了对象。 reloadData 方法再次调用表的委托(delegate)方法。