NSURLConnection在某些参数中返回Null

Question

This is my URL . I need to get data from this URL..it will return the value for english words..but if i give parameter like "Para Qué Volviste"..then it returns null..Please help me ..

My code is

 NSURLConnection * connectionGetISRC=[[NSURLConnection alloc]initWithRequest:[NSURLRequest requestWithURL:[NSURL URLWithString:@"http://ws.spotify.com/search/1/track.json?q=Para Qué Volviste"]] delegate:self];
    [connectionGetISRC start];


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

-(void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
    NSLog(@"dat %@",data);
    [dataJson appendData:data];
}

-(void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error
{
    NSLog(@"error %@",error.description);
    [hud hide:YES];
}

-(void)connectionDidFinishLoading:(NSURLConnection *)connection
{
    id dict=[NSJSONSerialization JSONObjectWithData:dataJson options:kNilOptions error:nil];
    NSLog(@"dataJson %@",dataJson);
    NSLog(@"dicvt %@",dict);
}

Answer 1

you should encode you request parameters before intiating connection like below,

NSString* urlString = [NSString stringWithFormat:@"http://ws.spotify.com/search/1/track.json?q=%@",[@"Para Qué Volviste" stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding]];

NSURL* url = [NSURL URLWithString:urlString];

NSURLConnection * connectionGetISRC=[[NSURLConnection alloc]initWithRequest:[NSURLRequest requestWithURL:[NSURL URLWithString:url] delegate:self];
[connectionGetISRC start];

Answer 2

look like the space in your URL a problem. try this connection srting

 NSString *str=[NSString stringWithFormat:@"http://ws.spotify.com/search/1/track.json?q=Para Qué Volviste"];
str=[str stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
NSURLConnection * connectionGetISRC=[[NSURLConnection alloc]initWithRequest:[NSURLRequest requestWithURL:[NSURL URLWithString:str]] delegate:self];
[connectionGetISRC start];

Answer 3

You want to percent-escape your URL's parameter, but take care to not be seduced by stringByAddingPercentEscapesUsingEncoding . That takes care of spaces fine (which is the immediate problem), but if you had some other reserved characters in it, it would fail (eg notably if your parameter had & or + characters in it). If you want to handle these sorts of characters, you really should use CFURLCreateStringByAddingPercentEscapes instead:

NSString* urlString = [NSString stringWithFormat:@"http://ws.spotify.com/search/1/track.json?q=%@", [self percentEscapeString:@"Para Qué Volviste"]];
NSURLConnection * connectionGetISRC=[[NSURLConnection alloc]initWithRequest:[NSURLRequest requestWithURL:[NSURL URLWithString:urlString] delegate:self];
// [connectionGetISRC start];

Where, percentEscapeString calls CFURLCreateStringByAddingPercentEscapes :

- (NSString *)percentEscapeString:(NSString *)string
{ 
    return CFBridgingRelease(CFURLCreateStringByAddingPercentEscapes(kCFAllocatorDefault,
                                                                     (CFStringRef)string,
                                                                     NULL,
                                                                     (CFStringRef)@":/?@!$&'()*+,;=",
                                                                     kCFStringEncodingUTF8));
}

As an aside, the initWithRequest:delegate: automatically starts the connection, so you should not be manually calling the start method. As the documentation for start says:

Calling this method is necessary only if you create a connection with the initWithRequest:delegate:startImmediately: method and provide NO for the startImmediately parameter.