How to send json data in the Http request using NSURLRequest

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

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.

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
         
     }
 }];

I would suggest to use ASIHTTPRequest

> ASIHTTPRequest is an easy to use > wrapper around the CFNetwork API that > makes some of the more tedious aspects > of communicating with web servers > easier. It is written in Objective-C > and works in both Mac OS X and iPhone > applications. > > It is suitable performing basic HTTP > requests and interacting with > REST-based services (GET / POST / PUT > / DELETE). The included > ASIFormDataRequest subclass makes it > easy to submit POST data and files > using multipart/form-data.

---

Please note, that the original author discontinued with this project. See the followring post for reasons and alternatives: http://allseeing-i.com/%5Brequest_release%5D;

Personally I am a big fan of AFNetworking

Most of you already know this by now, but I am posting this, just incase, some of you are still struggling with JSON in iOS6+.

In iOS6 and later, we have the NSJSONSerialization Class that is fast and has no dependency on including "outside" libraries.

NSDictionary *result = [NSJSONSerialization JSONObjectWithData:[resultStr dataUsingEncoding:NSUTF8StringEncoding] options:0 error:nil]; 

This is the way iOS6 and later can now parse JSON efficiently.The use of SBJson is also pre-ARC implementation and brings with it those issues too if you are working in an ARC environment.

I hope this helps!

Here is a great article using Restkit

It explains on serializing nested data into JSON and attaching the data to a HTTP POST request.

Since my edit to Mike G's answer to modernize the code was rejected 3 to 2 as

> This edit was intended to address the author of the post and makes no > sense as an edit. It should have been written as a comment or an > answer

I'm reposting my edit as a separate answer here. This edit removes the JSONRepresentation dependency with NSJSONSerialization as Rob's comment with 15 upvotes suggests.

    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"];
               
    NSLog(@"jsonRequest is %@", jsonRequest);
 
    NSURL *url = [NSURL URLWithString:@"https://xxxxxxx.com/questions"];
  
    NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url
                 cachePolicy:NSURLRequestUseProtocolCachePolicy timeoutInterval:60.0];
 
 
    NSData *requestData = [NSJSONSerialization dataWithJSONObject:dict options:0 error:nil]; //TODO handle error
 
    [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:

NSDictionary *jsonDict = [NSJSONSerialization JSONObjectWithData:data options:0 error:nil];
    NSDictionary *question = [jsonDict objectForKey:@"question"];

Here's an updated example that is using NSURLConnection +sendAsynchronousRequest: (10.7+, iOS 5+), The "Post" request remains the same as with the accepted answer and is omitted here for the sake of clarity:

NSURL *apiURL = [NSURL URLWithString:
    [NSString stringWithFormat:@"http://www.myserver.com/api/api.php?request=%@", @"someRequest"]];
NSURLRequest *request = [NSURLRequest requestWithURL:apiURL]; // this is using GET, for POST examples see the other answers here on this page
[NSURLConnection sendAsynchronousRequest:request
                                   queue:[NSOperationQueue mainQueue]
				 	   completionHandler:^(NSURLResponse *response, NSData *data, NSError *connectionError) {
	 if(data.length) {
		 NSString *responseString = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
		 if(responseString && responseString.length) {
			 NSLog(@"%@", responseString);
		 }
	 }
}];

> You can try this code for send json string

NSData *jsonData = [NSJSONSerialization dataWithJSONObject:ARRAY_CONTAIN_JSON_STRING options:NSJSONWritin*emphasized text*gPrettyPrinted error:NULL];
NSString *jsonString = [[NSString alloc] initWithData:jsonData encoding:NSUTF8StringEncoding];
NSString *WS_test = [NSString stringWithFormat:@"www.test.com?xyz.php&param=%@",jsonString];