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我试图解析来自 USGS 的 JSON 字符串。但是我收到错误"-[__NSCFDictionary objectAtIndex:]: unrecognized selector sent to instance 0x68a34c0"基本上，我想将 USGS JSON 解析到 tableview 中。任何人都可以帮忙吗？这是我的代码。

ViewController.h

@interface EarthquakeViewController : UITableViewController
{
    NSArray *json;
    NSDictionary *earthquakeReport;
}

ViewController.m

- (void)viewDidLoad
{
    //content = [NSMutableArray arrayWithObjects:@"one", @"two", nil];
    [super viewDidLoad];
    [self fetchReports];
}
- (void)fetchReports
{
    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
        NSData* data = [NSData dataWithContentsOfURL:
                        [NSURL URLWithString: @"http://earthquake.usgs.gov/earthquakes/feed/geojson/all/hour"]];

        NSError* error;
        json = [NSJSONSerialization JSONObjectWithData:data options:NSJSONReadingAllowFragments error:&error];
        NSLog(@"%@", json);
        dispatch_async(dispatch_get_main_queue(), ^{
            [self.tableView reloadData];
        });
    });
}
- (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 json.count;
}

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

    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
    if (cell == nil) {
        cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier];
    }
    earthquakeReport = [json objectAtIndex:indexPath.row];
    NSString *country = [[[earthquakeReport objectForKey:@"features"] objectForKey:@"properties"] objectForKey:@"place"];
    NSString *mag = [[[earthquakeReport objectForKey:@"features"] objectForKey:@"properties"] objectForKey:@"mag"];
    cell.textLabel.text = country;
    cell.detailTextLabel.text = mag;

    return cell;



}

错误显示在该行earthquakeReport = [json objectAtIndex:indexPath.row];

4

1 回答 1

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如果您在 Web 浏览器 ( http://earthquake.usgs.gov/earthquakes/feed/geojson/all/hour ) 中查看您的 JSON 数据，您应该注意到您尝试访问的数组不在根级别。根级别是字典，您要查找的数组位于“功能”键中。

要正确访问它，首先将您的jsonivar 声明更改为NSDictionary：

NSDictionary *json;

然后，在您的tableView:cellForRowAtIndexPath:方法中，这样访问报告：

earthquakeReport = [[json objectForKey:@"features"] objectAtIndex:indexPath.row];
于 2012-07-02T07:27:46.570 回答