Question

我在我的app中的异步线程上调用了Google的地理编码API和Distance Matrix API。但是它发出了NSRangeException。这是我的代码：

dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0),^
{
    NSString *urlStringGeoCoding;
    NSString *urlString;

    urlStringGeoCoding = [NSString stringWithFormat:@"http://maps.googleapis.com/maps/"
                                                    @"api/geocode/json?"
                                                    @"latlng=40.714224,-73.961452&sensor=true"];

    urlString = [NSString stringWithFormat:@"http://maps.googleapis.com"
                                           @"/maps/api/distancematrix/json?"
                                           @"origins=%@&destinations=%@&mode=driving&"
                                           @"language=en&sensor=true&units=imperial","
                                           @"current,@"Chicago,IL"];

    NSURL   *urlGeo = [NSURL URLWithString:[urlStringGeoCoding
                          stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding]];
    NSURL   *url    = [NSURL URLWithString:[urlString
                          stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding]];
    NSData  *googledatageo = [NSData dataWithContentsOfURL:urlGeo];
    NSData  *googledata    = [NSData dataWithContentsOfURL:url];
    NSError *errorgeo;
    NSError *error;

    NSMutableDictionary *json = [NSJSONSerialization JSONObjectWithData:googledata 
                                                                options:kNilOptions 
                                                                  error:&error];
    NSMutableDictionary *jsongeo = [NSJSONSerialization JSONObjectWithData:googledatageo 
                                                                   options:kNilOptions 
                                                                     error:&errorgeo];

    NSString *result = [[[[[[json objectForKey:@"rows"] objectAtIndex: 0] objectForKey:@"elements"] objectAtIndex:0]objectForKey:@"distance"]objectForKey:@"text"];
    if(jsongeo)
    {
       NSString *resultgeo = [[[jsongeo objectForKey:@"results"] objectAtIndex: 0] objectForKey:@"formatted_address"] ;
    }

    dispatch_sync(dispatch_get_main_queue(), ^
    {     
        cell.distanceLabel.text = result;
    });
});

这是我得到的错误：由于未捕获的异常终止应用程序＆＃39; NSRangeException＆＃39;，原因：＆＃39; * - [__ NSArrayI objectAtIndex：]：索引0超出空数组的范围＆＃39; * 第一次抛出调用堆栈：（0x289a012 0x2210e7e 0x284fb44 0x1318c 0x57f953f 0x580b014 0x57fc2e8 0x57fc450 0x9112ae72 0x91112d2a）

如何在此处阻止范围异常？

Answer 1

通过检查count，"rows"和"elements"数组的"results"，您可以在调用objectAtIndex:之前阻止这些范围异常。

分解result和resultgeo这两条非常长的行是个好主意;只需使用一些临时的NSArray变量。

调用JSON后超出边界的NSRangeException

1 个答案: