NSURLConnection data coming back empty - ios

Question

I can't figure out why my code isn't working. I think I'm doing everything correctly, the php script encodes and displays how it should. Can someone please look over my code and suggest what I'm doing wrong?
PHP:
$link = ...succesfully connects
if ($link){
if (isset($_REQUEST['past'])) {
$result = mysqli_query($link, 'SELECT * FROM messages WHERE id > '.
mysqli_real_escape_string($link, $_REQUEST['past']).
' ORDER BY added LIMIT 50');
$messages = array();
echo json_encode($messages);
} else {
$result = mysqli_query($link, 'SELECT * FROM messages ORDER BY timeadded LIMIT 50');
$messages = array();
while ($row = mysqli_fetch_assoc($result)) {
$messages[] = $row;
}
echo json_encode($messages);
}
}
The output is like this:
[{"id":"1","user":"me","message":"my first message","timeadded":"2014-02-11 12:47:55"},{"id":"2","user":"me","message":"my second message","timeadded":"2014-02-18 14:29:23"}]
Here's my ViewController code:
h:
{
NSMutableData *responseData;
}
#property (nonatomic, strong) NSMutableArray *receivedData;
m:
#synthesize receivedData;
- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{
[responseData setLength:0];
NSLog(#"received response");
}
- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
[responseData appendData:data];
NSLog(#"%#", receivedData);
}
- (void)connectionDidFinishLoading:(NSURLConnection *)connection
{
NSLog(#"Succeeded! Received %d bytes of data",[responseData length]);
receivedData = [NSJSONSerialization JSONObjectWithData:responseData options:kNilOptions error:nil];
NSLog(#"%#", responseData);
}
- (void)viewDidLoad
{
[super viewDidLoad];
[self getNewMessages];
}
- (void)getNewMessages {
NSURL *url = [NSURL URLWithString:[NSString stringWithFormat:#"messages.php?past=%d", lastId] relativeToURL:[NSURL URLWithString:#"http://www.mydomain.com/"]];
responseData = [NSMutableData dataWithCapacity:0];
NSMutableURLRequest *request = [[NSMutableURLRequest alloc] init];
[request setURL:url];
[request setHTTPMethod:#"GET"];
NSURLConnection *conn=[[NSURLConnection alloc] initWithRequest:request delegate:self];
if (conn)
{
receivedData = [[NSMutableArray alloc]init];
NSLog(#"sent request to server");
}
}
I'm just trying to log the array after it gets deserialized but it comes up empty in the log. The first two logs get displayed and then just (). What am I doing wrong here? The app builds and runs just fine, no errors...thanks in advance!
If I add a NSMutableData variable and try to do it like in the documentation, the data I get in the didReceiveData function look like this: <5b5d>. What does that mean?
Here's my response received:
{ status code: 200, headers {
Connection = "Keep-Alive";
"Content-Type" = "text/html";
Date = "Wed, 19 Feb 2014 00:03:30 GMT";
"Keep-Alive" = "timeout=10, max=30";
Server = Apache;
"Transfer-Encoding" = Identity;
Vary = "Accept-Encoding";
} }
ANSWER: So apparently the PHP script was wrong...it didn't like isset. Once I got rid of that, I got my data to return. Following the iOS documentation, everything worked like it should.

Answer 1

You're not using connection:didReceiveData: correctly. You should create an NSMutableData instance, and append the data received in connection:didReceiveData: to it. You should do the conversion to your array in connectionDidFinishLoading: which you haven't implemented. Look at the code Apple shows in the "URL Loading System Programming Guide" for an example.

Answer 2

Please refer the document for your reference from this link. https://developer.apple.com/library/mac/documentation/Cocoa/Conceptual/URLLoadingSystem/Tasks/UsingNSURLConnection.html
- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data {
// Append the new data to the instance variable you declared
[_responseData appendData:data];
}
- (void)connectionDidFinishLoading:(NSURLConnection *)connection {
// The request is complete and data has been received
// You can parse the stuff in your instance variable now
NSLog(#"%#", [NSJSONSerialization JSONObjectWithData:_responseData options:kNilOptions error:nil]);
}
- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error {
// The request has failed for some reason!
// Check the error var
}