NSURL *url = [NSURL URLWithString:@"itms-services://?action=download-manifest&url=https://xxxxxx.com/rest/images/apps/ipa/dev/xyz.plist"]];
[[UIApplication sharedApplication] openURL:url];
openUrl method was deprecated.
[[UIApplication sharedApplication] openURL: url options:@{} completionHandler:nil];
This method latest openUrl method and it will display prompt dialog.The dialog will show
xxxxxx.com would like to install "YOUR_APP_NAME"
this messages. If you click the "install" button application will close and ipa will download.