ios - 在 TableView 上通过NSURLSession读取数据

Question

我尝试使用NSURLSession读取数据并返回tableview，但是即使我的代码也在viewArray中添加了数据

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

返回0 !，这是我的代码:

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Initialize table data
    viewArray = [NSMutableArray arrayWithObjects: nil ];

    NSURLSession *session = [NSURLSession sharedSession];
    NSURLSessionDataTask *dataTask = [session dataTaskWithURL:[NSURL URLWithString:@"http://pizzy.sadrcom.com/foodCategories/pizzas/margarita"] completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {
        NSDictionary *json = [NSJSONSerialization JSONObjectWithData:data options:0 error:nil];
        NSLog(@"%@", json);
        for (NSDictionary* groups in json ) {
            GroupData *gInfo = [[GroupData alloc] init];
            // Title
            gInfo.title    = [groups objectForKey:@"Title"];
            // The Id
            gInfo.theId  = [groups objectForKey:@"Id"];

            [viewArray addObject:gInfo];
        }

    }];
    [dataTask resume];
}

Answer 1

在将对象添加到数组后，您没有调用[tableView reloadData];，并且随着数据异步的获取，那么第一次您的numberOfRowsInSection将在收到数据之前调用。
做这样的事情

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Initialize table data
    viewArray = [NSMutableArray arrayWithObjects: nil ];

    NSURLSession *session = [NSURLSession sharedSession];
    NSURLSessionDataTask *dataTask = [session dataTaskWithURL:[NSURL URLWithString:@"http://pizzy.sadrcom.com/foodCategories/pizzas/margarita"] completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {
    NSDictionary *json = [NSJSONSerialization JSONObjectWithData:data options:0 error:nil];
    NSLog(@"%@", json);
    for (NSDictionary* groups in json ) {
        GroupData *gInfo = [[GroupData alloc] init];
        // Title
        gInfo.title    = [groups objectForKey:@"Title"];
        // The Id
        gInfo.theId  = [groups objectForKey:@"Id"];
        [viewArray addObject:gInfo];

    }
        dispatch_async(dispatch_get_main_queue(), ^{
                [tableView reloadData];
            });
    }];
    [dataTask resume];

}