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    <p>A few things first</p> <ul> <li>Decide how you want to encode your data - JSON or url-encoding are a good start.</li> <li>Decide upon a return value - will it be 1, TRUE or 0, FALSE, or even YES/non-nil nothing/nil. </li> <li>Read up on the <a href="https://developer.apple.com/library/mac/#documentation/Cocoa/Conceptual/URLLoadingSystem/Tasks/UsingNSURLConnection.html#//apple_ref/doc/uid/20001836-BAJEAIEE">URL Loading System</a>, it's your friend. </li> </ul> <p>Aim to make all your url connections asynchronous so your UI remains responsive. You can do this with NSURLConnectionDelegate callbacks. NSURLConnection has a small drawback: your code must be decoupled. Any variables you want available in the delegate functions will need to be saved to ivars or in your request's userInfo dict. </p> <p>Alternatively you can use GCD, which, when coupled with the __block qualifiers, allows you to specify error/return code at the point you declare it - useful for one off fetches. </p> <p>Without further ado, here's a quick and dirty url-encoder: </p> <pre><code>- (NSData*)encodeDictionary:(NSDictionary*)dictionary { NSMutableArray *parts = [[NSMutableArray alloc] init]; for (NSString *key in dictionary) { NSString *encodedValue = [[dictionary objectForKey:key] stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding]; NSString *encodedKey = [key stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding]; NSString *part = [NSString stringWithFormat: @"%@=%@", encodedKey, encodedValue]; [parts addObject:part]; } NSString *encodedDictionary = [parts componentsJoinedByString:@"&amp;"]; return [encodedDictionary dataUsingEncoding:NSUTF8StringEncoding]; } </code></pre> <p>Using a JSON library like <a href="https://github.com/johnezang/JSONKit">JSONKit</a> makes encoding things easier, consider it!</p> <h2>Method 1 - NSURLConnectionDelegate async callbacks:</h2> <pre><code>// .h @interface ViewController : UIViewController&lt;NSURLConnectionDelegate&gt; @end // .m @interface ViewController () { NSMutableData *receivedData_; } @end ... - (IBAction)asyncButtonPushed:(id)sender { NSURL *url = [NSURL URLWithString:@"http://localhost/"]; NSDictionary *postDict = [NSDictionary dictionaryWithObjectsAndKeys:@"user", @"username", @"password", @"password", nil]; NSData *postData = [self encodeDictionary:postDict]; // Create the request NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url]; [request setHTTPMethod:@"POST"]; [request setValue:[NSString stringWithFormat:@"%d", postData.length] forHTTPHeaderField:@"Content-Length"]; [request setValue:@"application/x-www-form-urlencoded charset=utf-8" forHTTPHeaderField:@"Content-Type"]; [request setHTTPBody:postData]; NSURLConnection *connection = [[NSURLConnection alloc] initWithRequest:request delegate:self]; [connection start]; } - (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response { [receivedData_ setLength:0]; } - (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data { [receivedData_ appendData:data]; } - (void)connectionDidFinishLoading:(NSURLConnection *)connection { NSLog(@"Succeeded! Received %d bytes of data", [receivedData_ length]); NSString *responeString = [[NSString alloc] initWithData:receivedData_ encoding:NSUTF8StringEncoding]; // Assume lowercase if ([responeString isEqualToString:@"true"]) { // Deal with true return; } // Deal with an error } </code></pre> <h2>Method 2 - Grand Central Dispatch async function:</h2> <pre><code>// .m - (IBAction)dispatchButtonPushed:(id)sender { NSURL *url = [NSURL URLWithString:@"http://www.apple.com/"]; NSDictionary *postDict = [NSDictionary dictionaryWithObjectsAndKeys:@"user", @"username", @"password", @"password", nil]; NSData *postData = [self encodeDictionary:postDict]; // Create the request NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url]; [request setHTTPMethod:@"POST"]; [request setValue:[NSString stringWithFormat:@"%d", postData.length] forHTTPHeaderField:@"Content-Length"]; [request setValue:@"application/x-www-form-urlencoded charset=utf-8" forHTTPHeaderField:@"Content-Type"]; [request setHTTPBody:postData]; dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{ // Peform the request NSURLResponse *response; NSError *error = nil; NSData *receivedData = [NSURLConnection sendSynchronousRequest:request returningResponse:&amp;response error:&amp;error]; if (error) { // Deal with your error if ([response isKindOfClass:[NSHTTPURLResponse class]]) { NSHTTPURLResponse *httpResponse = (NSHTTPURLResponse*)response; NSLog(@"HTTP Error: %d %@", httpResponse.statusCode, error); return; } NSLog(@"Error %@", error); return; } NSString *responeString = [[NSString alloc] initWithData:receivedData encoding:NSUTF8StringEncoding]; // Assume lowercase if ([responeString isEqualToString:@"true"]) { // Deal with true return; } // Deal with an error // When dealing with UI updates, they must be run on the main queue, ie: // dispatch_async(dispatch_get_main_queue(), ^(void){ // // }); }); } </code></pre> <h2>Method 3 - Use an NSURLConnection convenience function</h2> <pre><code>+ (void)sendAsynchronousRequest:(NSURLRequest *)request queue:(NSOperationQueue *)queue completionHandler:(void (^)(NSURLResponse*, NSData*, NSError*))handler </code></pre> <p>Hope this helps.</p>
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    1. COvery nice description.
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    2. CO@Matt Which option would be best if i want to make 2 fetches from a web service, one for usersArray and another for userPoints array and use them to populate a detail type uitableviewcell?
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    3. CO@Matt, please see this post: http://stackoverflow.com/questions/17415191/how-are-nsoperation-gcd-nsurlconnection-calls-structured
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