使用Objective-C解析Echo Nest API JSON时出错

Question

我对Objective-C相对陌生，但我以前用JavaScript解析过JSON。

我的视图中有此代码DidLoad

NSURL *songsURL = [NSURL URLWithString:@"http://developer.echonest.com/api/v4/song/search?api_key=UVHRIOB9ISTKAAQ0R&format=json&results=1&combined=everybody%20dance%20now&bucket=id:7digital-UK&bucket=tracks&limit=true"];
NSData *jsonData = [NSData dataWithContentsOfURL:songsURL];
NSError *error = nil;
NSDictionary *dataDictionary = [NSJSONSerialization JSONObjectWithData:jsonData options:0 error:&error];
NSDictionary *item = [dataDictionary objectForKey:@"response"];
NSLog(@"%@", item);
NSDictionary *songs = [item objectForKey:@"songs"];
NSLog(@"%@", songs);
NSDictionary *songTitle = [songs objectForKey:@"title"];
NSLog(@"Title= %@", songTitle);

一切都很好，直到我试着找到歌曲的标题。

在我提取歌曲后，JSON看起来是这样的：

(
    {
    "artist_foreign_ids" =         (
                    {
            catalog = "7digital-UK";
            "foreign_id" = "7digital-UK:artist:2060042";
        }
    );
    "artist_id" = ARKSHFP12D5CD74F5D;
    "artist_name" = "Everybody Left";
    id = SOWGJIF143A016B701;
    title = "We Are Everybody Left";
    tracks =         (
                    {
            catalog = "7digital-UK";
            "foreign_id" = "7digital-UK:track:32612792";
            "foreign_release_id" = "7digital-UK:release:3062491";
            id = TRZNPMZ1429AA0B7CE;
            "preview_url" = "http://previews.7digital.com/clip/32612792";
            "release_image" = "http://artwork-    cdn.7static.com/static/img/sleeveart/00/030/624/0003062491_200.jpg";
        }
    );
 }
)

我已经尝试过获取其他值，例如使用NSDictionary *tracks = [songs objectForKey:@"tracks"];获取tracks，但仍然会收到一个错误：

2014-08-29 01:54:07.612 khord[9530:60b] -[__NSCFArray objectForKey:]: unrecognized selector sent to     instance 0x987c450
2014-08-29 01:54:07.614 khord[9530:60b] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[__NSCFArray objectForKey:]: unrecognized selector sent to instance 0x987c450'

有人能为我提供一个如何正确解析JSON的解决方案吗。我有一种感觉，我没有正确理解数据类型。

Answer 1

songs是一个字典数组，每个字典都有一个tracks键。

尝试：

[[songs objectAtIndex:0] valueForKey:@"tracks"]