iOS json无法从iTunes api检索数据

Question

I am using the following code to try to get the trackName from iTunes API. It should come from this link for example: https://itunes.apple.com/search?term=EMINEM&entity=song&limit=3 It keeps returning nothing (label is blank and it is not because the label is too small)

- (void)pressSearchKey {
    NSInteger numberOfResults = 3;
    NSString *searchString = self.keyboard.textField.text;

    NSString *encodedSearchString = [searchString stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
    NSString *finalSearchString = [NSString stringWithFormat:@"https://itunes.apple.com/lookup?term=%@&entity=song&limit=%ld",searchString,numberOfResults];

    NSURL *searchURL = [NSURL URLWithString:finalSearchString];
    dispatch_queue_t iTunesQueryQueue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);

    dispatch_async(iTunesQueryQueue, ^{
        NSError *error = nil;
        NSData *data = [[NSData alloc] initWithContentsOfURL:searchURL options:NSDataReadingUncached error:&error];

        if (data && !error) {
            NSDictionary *JSON = [NSJSONSerialization JSONObjectWithData:data options:NSJSONReadingMutableContainers error:nil];

            NSArray *array = [JSON objectForKey:@"results"];
            NSArray *arrayTracks;
            for (NSDictionary *bpDictionary in array) {
                arrayTracks = [bpDictionary objectForKey:@"trackName"];
            }
            dispatch_async(dispatch_get_main_queue(), ^{
                self.keyboard.firstLabel.text = [arrayTracks objectAtIndex:1];
            });
        }
    });
}

Answer 1

You've got a couple of problems in this one too.

1. You're never utilizing your encodedSearchString when building finalSearchString
2. Your example URL calls https://itunes.apple.com/ search whereas the URL in your code is https://itunes.apple.com/ lookup . Changing it to search returns the expected results.

Fixed:

NSInteger numberOfResults = 3;
NSString *searchString = @"EMINEM";

NSString *encodedSearchString = [searchString stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
NSString *finalSearchString = [NSString stringWithFormat:@"https://itunes.apple.com/search?term=%@&entity=song&limit=%ld",encodedSearchString,numberOfResults];

NSURL *searchURL = [NSURL URLWithString:finalSearchString];
dispatch_queue_t iTunesQueryQueue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);

dispatch_async(iTunesQueryQueue, ^{
    NSError *error = nil;
    NSData *data = [[NSData alloc] initWithContentsOfURL:searchURL options:NSDataReadingUncached error:&error];

    if (data && !error) {
        NSDictionary *JSON = [NSJSONSerialization JSONObjectWithData:data options:NSJSONReadingMutableContainers error:nil];

        NSArray *array = [JSON objectForKey:@"results"];
        NSArray *arrayTracks;
        for (NSDictionary *bpDictionary in array) {
            arrayTracks = [bpDictionary objectForKey:@"trackName"];
        }
        dispatch_async(dispatch_get_main_queue(), ^{
            NSLog(@"%@", [arrayTracks objectAtIndex:1]);
        });
    }
});