Consider X and Y are friends in Facebook and they both have installed an app in their respective phones. But they are not
Make sure your facebook app id is same in both developer page and info in xcode next, enable sandbox mode,and must fill canvas url [under app on facebook category] in developer page.
NSString *facebookID = @"Your friend facebook id";
NSMutableDictionary* params =
[NSMutableDictionary dictionaryWithObject:facebookID forKey:@"to"];
NSString *message = @"SOME_MESSAGE";
NSString *title = @"TITLE";
[FBWebDialogs presentRequestsDialogModallyWithSession:nil
message:message
title:title
parameters:params handler:^(FBWebDialogResult result, NSURL *resultURL, NSError *error) {
if (error)
{
// Case A: Error launching the dialog or sending request.
NSLog(@"Error sending request.");
}
else
{
if (result == FBWebDialogResultDialogNotCompleted)
{
// Case B: User clicked the "x" icon
NSLog(@"User canceled request.");
}
else
{
NSLog(@"Request Sent. %@", params);
}
}}];