Posting JSON in Objective-C

Question

I've got a fairly easy question today. I have an app that needs to send a simple JSON array to a remote server in the form of 2D GPS coordinates. The app will use the CoreLocation framework in order to generate these coordinates. For now, I want to hard code some sample coordinates to get the JSON right. However, I cannot seem to form the JSON correctly within the ObjC code.

Here is the code:

NSMutableURLRequest *request =
[NSMutableURLRequest requestWithURL:[NSURL URLWithString:@"http:myserver/handler/index"]];
[request setHTTPMethod:@"POST"];
NSString *jsonString = @"{"
@"  \"geo\": {"
@"    \"lat\": \"37.78\","
@"    \"lon\": \"-122.40";
NSData *jsonData = [jsonString dataUsingEncoding:NSUTF8StringEncoding];
    jsonString = [[NSString alloc] initWithData:jsonData encoding:NSUTF8StringEncoding];
[request setHTTPBody:jsonData];
(void)[[NSURLConnection alloc] initWithRequest:request delegate:self];

Here is what the server is expecting (but not receiving):

{
"geo": {
    "lat": "37.78",
    "lon": "-122.40"
}

I'm sure it's a simple JSON formatting issue or otherwise numskull move on my part.

Any help is always appreciated!

Answer 1

You are doing this the hard way. Create an NSDictionary then convert that to the desired JSON data:

NSDictionary *dictionary = @{ @"geo" : @{ @"lat" : @"37.78", @"lon" : @"-122.40" } };
NSError *error = nil;
NSData *jsonData = [NSJSONSerialization dataWithJSONObject:dictionary options:0 error:&error];
if (jsonData) {
    // process the data
} else {
    NSLog(@"Unable to serialize the data %@: %@", dictionary, error);
}

No need for the string at all.

Edit: If your real data is an array of objects then create an array of dictionaries or whatever structure you need. The rest is the same.