http://www.jianshu.com/p/db785c3f1603
拿到app id
NSString *iTunesString = [NSString stringWithFormat:@"http://itunes.apple.com/app/id%@", appid];
NSURL *iTunesURL = [NSURL URLWithString:iTunesString];
[[UIApplication sharedApplication] openURL:iTunesURL];
