Swift shouldSelectViewController 使用 alertController

Question

我有一个看似正常的用例:在选择某个选项卡(在我的例子中为“注销”)时，我想显示一个警告，要求在转换之前进行确认。这似乎应该在 shouldSelectViewController 函数中处理。但是，alertController 是异步的，我不得不在它完成之前返回一个 bool 值。 shouldSelectViewController 似乎不太可能在完成之前等待异步任务。有没有更好的地方让我在切换 View 之前触发我的确认警报？

这是我的代码:

func tabBarController(tabBarController: UITabBarController, shouldSelectViewController viewController: UIViewController) -> Bool {
    if (viewController is Trove.HomeViewController) {
        var shouldSelect = false
        let alertController = UIAlertController(title: "Logout", message: "Are you sure you want to log out?", preferredStyle: .Alert)
        let okAction = UIAlertAction(title: "Logout", style: .Default) { (action) in
            shouldSelect = true
        }
        alertController.addAction(okAction)
        let cancelAction = UIAlertAction(title: "Cancel", style: .Cancel) { (action) in }
        alertController.addAction(cancelAction)
        tabBarController.presentViewController(alertController, animated: true) { return shouldSelect}
    }
    return true
}

非常感谢任何帮助!谢谢!

Answer 1

您可以尝试设置 UITabBarController 的 selecedIndex 属性。

您的新if 语句:

if (viewController is Trove.HomeViewController) {
    let alertController = UIAlertController(title: "Logout", message: "Are you sure you want to log out?", preferredStyle: .Alert)
    let okAction = UIAlertAction(title: "Logout", style: .Default) { (action) in
        tabBarController.selectedIndex = 0 //CHANGE ME
    }
    alertController.addAction(okAction)
    let cancelAction = UIAlertAction(title: "Cancel", style: .Cancel) { (action) in }
    alertController.addAction(cancelAction)
    tabBarController.presentViewController(alertController, animated: true) 
    return false
}