Toran Billups Toran Billups - 24 days ago 5
Objective-C Question

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:@""]];
[[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)


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:@""];

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.