How to send json data in the Http request using NSURLRequest

Question

I'm new to objective-c and I'm starting to put a great deal of effort into request/response as of recent. I have a working example that can call a url (via http GET) and parse the json returned.

The working example of this is below

- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response {     [responseData setLength:0]; }  - (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data {     [responseData appendData:data]; }  - (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error {   NSLog([NSString stringWithFormat:@"Connection failed: %@", [error description]]); }  - (void)connectionDidFinishLoading:(NSURLConnection *)connection {     [connection release];   //do something with the json that comes back ... (the fun part) }  - (void)viewDidLoad {   [self searchForStuff:@"iPhone"]; }  -(void)searchForStuff:(NSString *)text {   responseData = [[NSMutableData data] retain];     NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:@"http://www.whatever.com/json"]];     [[NSURLConnection alloc] initWithRequest:request delegate:self]; } 

My first question is - will this approach scale up? Or is this not async (meaning I block the UI thread while the app is waiting for the response)

My second question is - how might I modify the request part of this to do a POST instead of GET? Is it simply to modify the HttpMethod like so?

[request setHTTPMethod:@"POST"]; 

And finally - how do I add a set of json data to this post as a simple string (for example)

{     "magic":{                "real":true             },     "options":{                "happy":true,                 "joy":true,                 "joy2":true               },     "key":"123" } 

Thank you in advance

Answer 1

Here's what I do (please note that the JSON going to my server needs to be a dictionary with one value (another dictionary) for key = question..i.e. {:question => { dictionary } } ):

NSArray *objects = [NSArray arrayWithObjects:[[NSUserDefaults standardUserDefaults]valueForKey:@"StoreNickName"],   [[UIDevice currentDevice] uniqueIdentifier], [dict objectForKey:@"user_question"],     nil]; NSArray *keys = [NSArray arrayWithObjects:@"nick_name", @"UDID", @"user_question", nil]; NSDictionary *questionDict = [NSDictionary dictionaryWithObjects:objects forKeys:keys];  NSDictionary *jsonDict = [NSDictionary dictionaryWithObject:questionDict forKey:@"question"];  NSString *jsonRequest = [jsonDict JSONRepresentation];  NSLog(@"jsonRequest is %@", jsonRequest);  NSURL *url = [NSURL URLWithString:@"https://xxxxxxx.com/questions"];  NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url              cachePolicy:NSURLRequestUseProtocolCachePolicy timeoutInterval:60.0];   NSData *requestData = [jsonRequest dataUsingEncoding:NSUTF8StringEncoding];  [request setHTTPMethod:@"POST"]; [request setValue:@"application/json" forHTTPHeaderField:@"Accept"]; [request setValue:@"application/json" forHTTPHeaderField:@"Content-Type"]; [request setValue:[NSString stringWithFormat:@"%d", [requestData length]] forHTTPHeaderField:@"Content-Length"]; [request setHTTPBody: requestData];  NSURLConnection *connection = [[NSURLConnection alloc]initWithRequest:request delegate:self]; if (connection) {  receivedData = [[NSMutableData data] retain]; } 

The receivedData is then handled by:

NSString *jsonString = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding]; NSDictionary *jsonDict = [jsonString JSONValue]; NSDictionary *question = [jsonDict objectForKey:@"question"]; 

This isn't 100% clear and will take some re-reading, but everything should be here to get you started. And from what I can tell, this is asynchronous. My UI is not locked up while these calls are made. Hope that helps.

Answer 2

I struggled with this for a while. Running PHP on the server. This code will post a json and get the json reply from the server

NSURL *url = [NSURL URLWithString:@"http://example.co/index.php"]; NSMutableURLRequest *rq = [NSMutableURLRequest requestWithURL:url]; [rq setHTTPMethod:@"POST"]; NSString *post = [NSString stringWithFormat:@"command1=c1&command2=c2"]; NSData *postData = [post dataUsingEncoding:NSASCIIStringEncoding]; [rq setHTTPBody:postData]; [rq setValue:@"application/x-www-form-urlencoded" forHTTPHeaderField:@"Content-Type"]; NSOperationQueue *queue = [[NSOperationQueue alloc] init];  [NSURLConnection sendAsynchronousRequest:rq queue:queue completionHandler:^(NSURLResponse *response, NSData *data, NSError *error)  {      if ([data length] > 0 && error == nil){          NSError *parseError = nil;          NSDictionary *dictionary = [NSJSONSerialization JSONObjectWithData:data options:0 error:&parseError];          NSLog(@"Server Response (we want to see a 200 return code) %@",response);          NSLog(@"dictionary %@",dictionary);      }      else if ([data length] == 0 && error == nil){          NSLog(@"no data returned");          //no data, but tried      }      else if (error != nil)      {          NSLog(@"there was a download error");          //couldn't download       }  }];