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用uinavigationcontroller__准备Segue交换机更好的方法?

segue switch-statement uinavigationcontroller swift

Ashley Mills · 技术社区 · 7 年前

我有几段介绍模态视图控制器。

class ProfileViewController: UIViewController {
    func configure(profile: Profile) { 
        // Some ProfileViewController specific config
    }
}

class SettingsViewController: UIViewController {
   func configure(settings: Settings) { 
        // Some SettingsViewController specific config
    }
}

这里有一些非常标准的代码,我们已经写了很多次了。

override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
    switch segue.destination {
    case let nav as UINavigationController:
        switch nav.topViewController {
        case let pvc as ProfileViewController:

            pvc.configure(profile: profile)
        case let svc as SettingsViewController:

            svc.configure(settings: settings)
        default:
            break
        }
    default:
        break
    }
}

我也试过这个方法

override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
    switch segue.destination {
    case let nav as UINavigationController
        where nav.topViewController is ProfileViewController:

        (nav.topViewController as! ProfileViewController).configure(profile: profile)
    case let nav as UINavigationController
        where nav.topViewController is SettingsViewController:

        (nav.topViewController as! SettingsViewController).configure(settings: settings)
    default:
        break
    }
}

但我想做的是两者的结合

override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
    switch segue.destination {
    case let nav as UINavigationController
        where let pvc = nav.topViewController as ProfileViewController:

        pvc.configure(profile: profile)
    case let nav as UINavigationController
        where let svc = nav.topViewController as SettingsViewController:

        svc.configure(settings: settings)
    default:
        break
    }
}

但显然,这不会编译。有人遇到过更好的模式吗?

更新

在下面扩展@serj的答案

extension UIStoryboardSegue {
    var destinationNavTopViewController: UIViewController? {
        return (destination as? UINavigationController)?.topViewController
    }
}

然后

override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
    switch (segue.destination, destinationNavTopViewController) {
    case let (_, pvc as ProfileViewController):

        pvc.configure(profile: profile)
    case let (_, svc as SettingsViewController):

        svc.configure(settings: settings)
    case let (ovc as OtherViewController, _):
        ovc.configureâ¦
    default:
        break
    }
}

1 回复 | 直到 7 年前

Serj 7 年前

当问到如何考虑两种情况时:

关于您想要实现什么的特定用例
更通用的用例 switch 声明

现在对于特定的用例,您似乎只希望在打开 segue.destination 当你有导航控制器的时候。你可以用一个 if let 或 guard let 如下所示:

guard let navigationController = segue.destination as? UINavigationController else { return }
guard let topController = navigationController.topViewController else { return }
switch topController {
  case let profileViewController as ProfileViewController:
    print("Do something for profile view controller")
  default:
    break
}

第二种情况更为普遍,是关于如何在switch语句中同时使用这两个变量。答案是元组。例如,我将提供一个来自苹果文档的示例,然后为您的特定用例提供一个示例。

let anotherPoint = (2, 0)
switch anotherPoint {
case (let x, 0):
    print("on the x-axis with an x value of \(x)")
case (0, let y):
    print("on the y-axis with a y value of \(y)")
case let (x, y):
    print("somewhere else at (\(x), \(y))")
}

现在,对于如何通过用例实现上述目标的示例,我们可以警告它:一个丑陋的示例可以得到改进,但可以说明问题:

switch (segue.destination, (segue.destination as? UINavigationController)?.topViewController) {
case (let nav as UINavigationController, let viewController as ProfileViewController):
    return
// Maybe the destination wasn't a nav maybe it was the sign in view controller and you don't care about the second variable
case (let signInController as SignInViewController, let _):
    return
default:
    return
}

这就是switch语句能够如此轻松地切换元组的能力。我希望我的例子能回答你的问题。我试图用所有含糊不清的词句来涵盖问题的所有部分。