json元素未传递到表视图

Question

我有一个简单的JSON提要，我可以解析它并在控制台中看到它，但我似乎无法将它显示在我的表视图中。我使用的是Xcode 5.0.2。我不确定为什么在回显到控制台时可以在for循环中看到它，而在表视图中却看不到它。

[
    {
        "first_name": "Bill"
    },
    {
        "first_name": "Ted"
    },
    {
        "first_name": "George"
    } etc...
]

#import 
#import "DisplayViewController.h"

@interface PhotosTableViewController : UITableViewController {

    IBOutlet UITableView *mainTableView;

   NSArray *news;
   NSMutableData *data;

}

@end

PhotoTableViewController.m

@interface PhotosTableViewController () {
    NSMutableArray *photos;
    NSArray *_locations;

}

   - (void)viewDidLoad
{

    NSURL *url = [NSURL URLWithString:@"http://feedurl.json"];
    NSURLRequest *request = [NSURLRequest requestWithURL:url];
    [[NSURLConnection alloc] initWithRequest:request delegate:self];

}

// some code left out for brevity


- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
    // Return the number of sections.
    return 1;
}

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
    // Return the number of rows in the section.
    //return photos.count;
    NSLog(@"news count: %lu", news.count);

    return news.count;
}


- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    static NSString *CellIdentifier = @"Cell";
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier forIndexPath:indexPath];

    cell.textLabel.text = [[photos objectAtIndex:indexPath.row] objectForKey:@"first_name"];
    NSLog(@"anything: %@", [[photos objectAtIndex:indexPath.row] objectForKey:@"first_name"] );


    return cell;

}



- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{
    data = [[NSMutableData alloc] init];
}

- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)theData
{
    [data appendData:theData];
}

- (void)connectionDidFinishLoading:(NSURLConnection *)connection
{
    [UIApplication sharedApplication].networkActivityIndicatorVisible = NO;

    news = [NSJSONSerialization JSONObjectWithData:data options:0 error:nil];

    NSDictionary *first_name;

   for (int i=0; i (cant put less than sign here breaks code view) [news count] i++)
    {
        first_name = [news objectAtIndex:i];
        NSLog(@"Statuses: %@", [first_name objectForKey:@"first_name"]);
   }


    [mainTableView reloadData];

}

-(void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error
{
    UIAlertView *errorView = [[UIAlertView alloc] initWithTitle:@"Error" message:@"The download could not complete - please make sure you're connected to the internet." delegate:nil cancelButtonTitle:@"Dismiss" otherButtonTitles:nil];

    [errorView show];
    [UIApplication sharedApplication].networkActivityIndicatorVisible = NO;
}

Answer 1

通过检查，您的代码看起来正常。您似乎没有使用UITableViewController子类，因为您有名为tableview，所以您必须在Interface Builder或代码中设置dataSource和delegate属性。在IB中，右键单击tableView对象，在connections列表的顶部有delegate和dataSource出口。从圆形拖动到viewController。在代码中，您可以在.m文件中这样做：

// Claim that your view controller conforms to the tableview protocols
@interface YourViewControllerClass () <UITableViewDataSource, UITableViewDelgate>
...
// somewhere early on, like in viewDidLoad or viewDidAppear or other initialization code
mainTableView.delegate = self;
mainTableView.dataSource = self;

当我遇到这些问题时，我倾向于在tableView方法中添加NSLogs以查看它们是否被调用。