Here is the code. I took it from http://www.whatsapp.com/faq/en/iphone/23559013 It goes into if condition. But do nothing. This code worked for iphone 5. And in case of iphone 5s nothing happened. It is not opening Whatsapp URL.
NSURL *whatsappURL = [NSURL URLWithString:@"whatsapp://send?text=Hello%2C%20World!"];
if ([[UIApplication sharedApplication] canOpenURL: whatsappURL]) {
[[UIApplication sharedApplication] openURL: whatsappURL];
}