Assign single line json element to label in Objective-c - objective-c

Question

I'm trying to assign a simple json feed element to a label.
My json feed that looks like this:
[{"code":501,"data":{"req":"0"}}]
My code after I've retrieved it from a url:
NSURLResponse *response;
NSData *POSTReply = [NSURLConnection sendSynchronousRequest:request returningResponse:&response error:nil];
NSString *theReply = [[NSString alloc] initWithBytes:[POSTReply bytes] length:[POSTReply length] encoding: NSASCIIStringEncoding];
NSLog(#"Reply: %#", theReply);
NSArray* json_object = [NSJSONSerialization
JSONObjectWithData:POSTReply
options:0
error:nil];
NSArray *json_object_line = [json_object objectAtIndex:0];
mainLabel.Text= [json_object_line valueForKey:#"code"];
There is no way I can get this to work. The app simply crashes unless I remove the last 2 lines. I've tried a lot of other options (especially for the last 2 lines) to no avail.
Is there anything I'm doing wrong?

Answer 1

You tried to assign NSNumber to the label's text property. It's a reason of the crash. The proper way is to get a formatted string from JSON field:
NSURLResponse *response;
NSData *POSTReply = [NSURLConnection sendSynchronousRequest:request
returningResponse:&response error:nil];
NSString *theReply = [[NSString alloc] initWithBytes:POSTReply.bytes
length:POSTReply.length
encoding:NSASCIIStringEncoding];
NSArray* json_object = [NSJSONSerialization JSONObjectWithData:POSTReply
options:0
error:nil];
NSDictionary *json_object_line = json_object[0];
mainLabel.text= [NSString stringWithFormat:#"%#", json_object_line[#"code"]];