ios - 如何在转到另一个 View Controller 时停止后台调用？

Question

如果不使用定时器概念，我不知道如何停止这个调用。今天，在尝试分析项目时，我发现由于以下功能每次分配内存都会增加:

func startAnimation(index: Int) {
    UIView.animate(withDuration: 4.0, delay: 0.5, options:[UIViewAnimationOptions.allowUserInteraction, UIViewAnimationOptions.curveEaseInOut], animations: {
        self.view.backgroundColor = self.colors[index]
    }) { (finished) in
        var currentIndex = index + 1
        if currentIndex == self.colors.count { currentIndex = 0 }
        self.startAnimation(index: currentIndex)
    }
}

Answer 1

做一件简单的事，提一个flag，

最初它应该，

var isViewDissappear = false

然后，

override func viewWillDisappear(_ animated: Bool) {
        super.viewWillDisappear(animated)

        isViewDissappear = true
    } 

然后再次调用时检查该标志，

func startAnimation(index: Int) {
        UIView.animate(withDuration: 4.0, delay: 0.5, options:[UIViewAnimationOptions.allowUserInteraction, UIViewAnimationOptions.curveEaseInOut], animations: {
            self.view.backgroundColor = self.colors[index]
        }) { (finished) in
            var currentIndex = index + 1
            if currentIndex == self.colors.count { currentIndex = 0 }
            if !self.isViewDissappear {
                self.startAnimation(index: currentIndex)
            }
        }
    }

就是这样。