How to check JSON post return value - objective-c

Question

I am new to JSON and I am trying to send a post I am wondering if how can I check if I did it properly or check the return value of it. Here's what I've done
NSURL *url = [NSURL URLWithString:#"http://json.myurl.com/.....];
NSMutableURLRequest *request = [[NSMutableURLRequest alloc] initWithURL:url];
NSDictionary *tmp = [[NSDictionary alloc] initWithObjectsAndKeys:
#"email", #"Email",
#"password", #"FirstName",
nil];
NSError *error;
NSData *postdata = [NSJSONSerialization dataWithJSONObject:tmp options:0 error:&error];
[request setHTTPBody:postdata];

Answer 1

For a beginner, I would recommend using third party framework, widely used by iOS developers across the world, called AFNetworking.
By using AFNetworking, HTTP requests are simple as that:
AFHTTPSessionManager *manager = [[AFHTTPSessionManager alloc] initWithSessionConfiguration:[NSURLSessionConfiguration defaultSessionConfiguration]];
[manager POST:url parameters:parameters progress:nil success:^(NSURLSessionDataTask *task, id responseObject) {
// TODO: Parse success here!
} failure:^(NSURLSessionDataTask * _Nullable task, NSError * _Nonnull error) {
// TODO: Parse failure here!
}];
In given example, object responseObject is a representation of API response JSON object.
Installation and further usage instructions of AFNetworking can be found in their website.

Answer 2

To check JSON POST return value:
NSString *strUrl=[NSString stringWithFormat:#"http://json.myurl.com/....."];
NSString *webStringURL = [strUrl stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
NSURL *url = [NSURL URLWithString:webStringURL];
NSMutableURLRequest *request = [[NSMutableURLRequest alloc] init];
NSDictionary *tmp = [[NSDictionary alloc] initWithObjectsAndKeys:
#"email", #"Email",
#"password", #"FirstName",
nil];
NSError* error;
NSData* postData = [NSJSONSerialization dataWithJSONObject:tmp options:NSJSONWritingPrettyPrinted error: &error];
NSString *postLength = [NSString stringWithFormat:#"%lu", (unsigned long)[postData length]];
[request setURL:url];
[request setHTTPMethod:#"POST"];
[request setValue:postLength forHTTPHeaderField:#"Content-Length"];
[request setHTTPBody:postData];
[NSURLConnection sendAsynchronousRequest:request queue:[[NSOperationQueue alloc]init] completionHandler:^(NSURLResponse *response, NSData *jsonData, NSError *error)
{
if (!error)
{
NSDictionary *jsonResponse = [NSJSONSerialization JSONObjectWithData:jsonData options:NSJSONReadingMutableLeaves error:&error];
dispatch_async(dispatch_get_main_queue(),^
{
NSLog(#"jsonResponse--->%#",jsonResponse);
});
}
else
{
dispatch_async(dispatch_get_main_queue(),^
{
NSLog(#"error--->%#",error.description);
});
}
}];
And to check you JSON format is correct or not go through this link