ios - 如何在 iOS7 中不启动方法

Question

只有当 >= 8.0 时，我才能开始下面的方法？它在 TabBarController 类中。

let floatVersion = (UIDevice.currentDevice().systemVersion as NSString).floatValue

func tabBarController(tabBarController: UITabBarController, animationControllerForTransitionFromViewController fromVC: UIViewController, toViewController toVC: UIViewController) -> UIViewControllerAnimatedTransitioning? {
    //   if ( floatVersion >= 8.0) {

    let transitioningObject: TransitioningObject = TransitioningObject()
    transitioningObject.tabBarController = self
    return transitioningObject
    //}
}

Answer 1

由于您的方法返回可选的 UIViewControllerAnimatedTransitioning，如果版本低于 8.0，您可以返回 nil

func tabBarController(tabBarController: UITabBarController, animationControllerForTransitionFromViewController fromVC: UIViewController, toViewController toVC: UIViewController) -> UIViewControllerAnimatedTransitioning? {
   if ( floatVersion >= 8.0) {

       let transitioningObject: TransitioningObject = TransitioningObject()
       transitioningObject.tabBarController = self
       return transitioningObject
    }else{
       return nil
    }
}