[iphone] 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

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];

Here is a great article using Restkit

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

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);
         }
     }
}];

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!

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

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"];

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

     }
 }];