ios - 如何在iOS7中不启动方法

只有当I s>=8.0时，我如何才能启动以下方法？
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
    //}
}

最佳答案

检查this response以验证系统版本。
您已经在正确的轨道上了，只需像处理if一样处理iOS >= 8.0，否则调用iOS7替代项并返回nil

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
    }else {
      //do something else here if it's iOS7 or earlier?
    }
    return nil
}