Objective C - POST data using NSURLConnection

Question

I\'m very slowly working my way through learning the URL loading system for iOS development, and I am hoping someone could briefly explain the following piece of code:

Answer 1

please use below code.
+(void)callapi:(NSString *)str withBlock:(dictionary)block{

NSData *postData = [str dataUsingEncoding:NSASCIIStringEncoding allowLossyConversion:YES];
NSString *postLength = [NSString stringWithFormat:@"%lu",(unsigned long)[postData length]];

NSMutableURLRequest *urlRequest = [NSMutableURLRequest requestWithURL:[NSURL URLWithString:[NSString stringWithFormat:@“%@/url”,WebserviceUrl]]
                                                          cachePolicy:NSURLRequestUseProtocolCachePolicy
                                                      timeoutInterval:120.0];

[urlRequest setHTTPMethod:@"POST"];
[urlRequest setValue:postLength forHTTPHeaderField:@"Content-Length"];
[urlRequest setValue:@"application/x-www-form-urlencoded" forHTTPHeaderField:@"Content-Type"];
[urlRequest setHTTPBody:postData];

[NSURLConnection sendAsynchronousRequest:urlRequest queue:[NSOperationQueue mainQueue] completionHandler:^(NSURLResponse *response, NSData *data, NSError *connectionError)
 {
     if (!data) {
         NSMutableDictionary *dict = [[NSMutableDictionary alloc] init];
          [dict setObject:[NSString stringWithFormat:@"%@",AMLocalizedString(SomethingWentWrong, nil)] forKey:@"error"];
         block(dict);
         return ;
     }
     NSError *error = nil;
     NSDictionary *dict = [NSJSONSerialization JSONObjectWithData:data options:NSJSONReadingAllowFragments error:&error];
     //////NSLog(@"%@",dict);
     if (!dict) {
         NSMutableDictionary *dict = [[NSMutableDictionary alloc] init];
         [dict setObject:AMLocalizedString(ServerResponceError, nil) forKey:@"error"];
         block(dict);
         return ;
     }
     block(dict);

 }];
}