Is retina display / detect retina display or not

detect that it is retina display or not

+ (BOOL)isRetineDisplay{
    if ([[UIScreen mainScreen] respondsToSelector:@selector(displayLinkWithTarget:selector:)] &&
        ([UIScreen mainScreen].scale == 2.0)) {
        // Retina display
        return YES;
    } else {
        // not Retine display
        return NO;
    }
}