The page I want to open using twitter app:
https://twitter.com/#!/PAGE
To open twitter app I use the following code:
The following code opens twitter page on twitter app if it is already installed, otherwise opens twitter on safari:
NSURL *twitterURL = [NSURL URLWithString:@"twitter://user?screen_name=username"];
if ([[UIApplication sharedApplication] canOpenURL:twitterURL])
[[UIApplication sharedApplication] openURL:twitterURL];
else
[[UIApplication sharedApplication] openURL:[NSURL URLWithString:@"http://www.twitter.com/username"]];
Don't forget to replace 'username' with your name.