Issue in NSURL in Objective C - ios

Question

I am trying to execute a async http request. but the call back log is not working. please analyze the code and suggest me the cause of this issue. I have seen the class examples in many places. But here i am calling it from a main function.
#interface HTTP : NSObject
#property (nonatomic,retain) NSMutableData *receivedData;
- (void) get : (NSString *) urlString;
#end
#implementation HTTP
#synthesize receivedData;
- (void)get: (NSString *)urlString {
NSLog ( #"GET: %#", urlString );
self.receivedData = [[NSMutableData alloc] init];
NSURLRequest *request = [[NSURLRequest alloc]
initWithURL: [NSURL URLWithString:urlString]
cachePolicy: NSURLRequestReloadIgnoringLocalCacheData
timeoutInterval: 10
];
NSURLConnection *connection = [[NSURLConnection alloc]
initWithRequest:request
delegate:self
startImmediately:YES];
[connection start];
}
- (void)connection:(NSURLConnection*) connection didReceiveResponse:(NSURLResponse *)response
{
NSLog(#"Response recieved");
}
- (void)connection:(NSURLConnection*) connection didReceiveData:(NSData *)data
{
NSLog(#"Data recieved");
NSString* responseString = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
[receivedData appendData:responseString];
}
#end
int main(const int c , char *arg[]){
HTTP *http = [[HTTP alloc] init];
[http get:#"http://www.apple.com"];
return 0;
}

Answer 1

Your program does not have a "run loop", therefore it terminates immediately after
[http get:#"http://www.apple.com"];
has returned, before any delegate functions are called. (Note that NSURLConnection works asynchronously.)
If this is for a stand-alone OS X application, you could to the following:
int main(const int c , char *arg[]){
HTTP *http = [[HTTP alloc] init];
[http get:#"http://www.apple.com"];
NSRunLoop *theRL = [NSRunLoop currentRunLoop];
while (shouldKeepRunning && [theRL runMode:NSDefaultRunLoopMode beforeDate:[NSDate distantFuture]]);
return 0;
}
where shouldKeepRunning is a (global) Boolean variable that is initially YES, and set to NO in
- (void)connectionDidFinishLoading:(NSURLConnection *)connection
{
shouldKeepRunning = NO;
}
and also in connection:didFailWithError:. Or you add a Boolean property loading to your HTTP class.
If this is for an iOS application or a OS X Cocoa application, then you already have a run loop and don't have to add your own.

Answer 2

/*
Till the application finishes loading, the main thread is kept alive so that the delegate methods are called.
Hence the while loop below.
*/
while(!finished) {
[[NSRunLoop currentRunLoop] runMode:NSDefaultRunLoopMode beforeDate:[NSDate distantFuture]];
}
Here is my working code.
#implementation HTTP
#synthesize receivedData,retStr,delegate;
- init {
if ((self = [super init])) {
receivedData = [[NSMutableData alloc] init];
}
return self;
}
- (void)get: (NSString *)urlString {
NSLog ( #"GET: %#", urlString );
self.receivedData = [[NSMutableData alloc] init];
NSURLRequest *request = [[NSURLRequest alloc]
initWithURL: [NSURL URLWithString:urlString]
cachePolicy: NSURLRequestReloadIgnoringLocalCacheData
timeoutInterval: 10
];
NSURLConnection *connection = [[NSURLConnection alloc]
initWithRequest:request
delegate:self
startImmediately:YES];
while(!finished) {
[[NSRunLoop currentRunLoop] runMode:NSDefaultRunLoopMode beforeDate:[NSDate distantFuture]];
}
if(!connection) {
NSLog(#"connection failed :(");
} else {
NSLog(#"connection succeeded :)");
}
}
- (void)post:(NSString*)urlString: (NSString*)body: (NSObject*) sender {
// POST
NSMutableString* requestURL = [[NSMutableString alloc] init];
[requestURL appendString:urlString];
NSMutableString* requestBody = [[NSMutableString alloc] initWithString:body];
NSMutableURLRequest *request = [[NSMutableURLRequest alloc] initWithURL: [NSURL URLWithString: [NSString stringWithString:requestURL]]];
NSString* requestBodyString = [NSString stringWithString:requestBody];
NSData *requestData = [NSData dataWithBytes: [requestBodyString UTF8String] length: [requestBodyString length]];
[request setHTTPMethod: #"POST"];
[request setValue:#"text/html; charset=utf-8" forHTTPHeaderField:#"Content-Type"];
[request setHTTPBody: requestData];
NSURLConnection *postConn= [[NSURLConnection alloc] initWithRequest:request delegate:sender];
/*
Till the application finishes loading, the main thread is kept alive so that the delegate methods are called.
Hence the while loop below.
*/
while(!finished) {
[[NSRunLoop currentRunLoop] runMode:NSDefaultRunLoopMode beforeDate:[NSDate distantFuture]];
}
if(!postConn) {
NSLog(#"POST connection failed :(");
} else {
NSLog(#"POST connection succeeded :)");
}
}
// ====================
// Callbacks
// ====================
#pragma mark NSURLConnection delegate methods
- (NSURLRequest *)connection:(NSURLConnection *)connection
willSendRequest:(NSURLRequest *)request
redirectResponse:(NSURLResponse *)redirectResponse {
NSLog(#"Connection received data, retain count");
return request;
}
- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response {
NSLog(#"Received response: %#", response);
[receivedData setLength:0];
}
- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data {
NSLog(#"Received %lu bytes of data", [data length]);
[receivedData appendData:data];
NSLog(#"Received data is now %lu bytes", [receivedData length]);
}
- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error {
NSRunAlertPanel(#"Error",[NSString stringWithFormat:#"Could not connect to server.Following error occured:\n\n%#", error], nil, nil, nil);
NSLog(#"Error receiving response: %#", error);
}
- (void)connectionDidFinishLoading:(NSURLConnection *)connection {
// Once this method is invoked, "responseData" contains the complete result
NSLog(#"Succeeded! Received %lu bytes of data", [receivedData length]);
NSString *dataStr=[[NSString alloc] initWithData:receivedData encoding:NSASCIIStringEncoding] ;
retStr = [NSString stringWithString:dataStr];
finished =TRUE;
// [self returnDcString:dataStr];
// NSLog(#"%#",dataStr);
if ([delegate respondsToSelector:#selector(didFinishDownload:)]) {
NSLog(#"Calling the delegate");
//NSString* dataAsString = [[[NSString alloc] initWithData:receivedData encoding:NSUTF8StringEncoding] autorelease];
// [delegate performSelector:#selector(didFinishDownload:) withObject: dataStr];
}
}
- (void)setDelegate:(id)val
{
delegate = val;
}
- (id)delegate
{
return delegate;
}
#end