在方向改变之前执行功能

Question

当方向改变时，是否可以执行一个功能并等待它直到完成执行然后执行旋转？这样的事情：

override func viewWillTransitionToSize(size: CGSize, withTransitionCoordinator coordinator: UIViewControllerTransitionCoordinator) {
        super.viewWillTransitionToSize(size, withTransitionCoordinator: coordinator)

         doStuff()

        // block until doStuff is done
        weak var weakSelf = self
        coordinator.animateAlongsideTransition({ (UIViewControllerTransitionCoordinatorContext) -> Void in

            }, completion: { (UIViewControllerTransitionCoordinatorContext) -> Void in  

        })
    }

Answer 1

Swift 3

func doStuff(check:(_ Check : Bool)->Void){

    check(true)
}

和viewWillTransitionToSize内部func：

doStuff { (myCheck) in
        if myCheck{

            // do something
        }
    }