I am developing an iPhone application for jail broken phones and in this application I would like to fetch user's phone number.
I have gone through the entire stackoverflow.com and found some relevant answers but all of them are obsolete and doesn't work with iOS 4.0 anymore.
The most famous solution for this problem is
NSString *num = [[NSUserDefaults standardUserDefaults] stringForKey:@"SBFormattedPhoneNumber"];
If you're targeting jailbroken phones, you might take a look at the CoreTelephony framework. I don't often work with private APIs, so no guarantees this particular framework makes the phone number available to you, but you might get lucky.