如何在 Swift 中显示来自另一个 class 的警报?
How to show an alert from another class in Swift?
我有一个主要的 class、AddFriendsController
,它运行以下代码行:
ErrorReporting.showMessage("Error", msg: "Could not add student to storage.")
然后我有这个 ErrorReporting.swift
文件:
导入基金会
class ErrorReporting {
func showMessage(title: String, msg: String) {
let alert = UIAlertController(title: title, message: msg, preferredStyle: UIAlertControllerStyle.Alert)
alert.addAction(UIAlertAction(title: "Ok", style: UIAlertActionStyle.Default, handler: nil))
self.presentViewController(alert, animated: true, completion: nil)
}
}
显然,self
在这里不起作用,并且给我一个错误。我如何引用当前打开的视图控制器(即在这种情况下 AddFriendsController
),因为我希望在许多不同的 swift 文件中使用相同的方法?
谢谢。
实际上,在我看来,视图控制器呈现操作应该在 UIViewController
实例上完成,而不是在模型 class.
上完成
一个简单的解决方法是将 UIViewController
实例作为参数传递
class ErrorReporting {
func showMessage(title: String, msg: String, `on` controller: UIViewController) {
let alert = UIAlertController(title: title, message: msg, preferredStyle: UIAlertControllerStyle.Alert)
alert.addAction(UIAlertAction(title: "Ok", style: UIAlertActionStyle.Default, handler: nil))
controller.presentViewController(alert, animated: true, completion: nil)
}
}
然后像下面这样称呼它
ErrorReporting.showMessage("Error", msg: "Could not add student to storage.", on: self)
您可以为 UIApplication 创建扩展方法(例如),它将 return 您的 topViewController:
extension UIApplication {
static func topViewController(base: UIViewController? = UIApplication.sharedApplication().delegate?.window??.rootViewController) -> UIViewController? {
if let nav = base as? UINavigationController {
return topViewController(nav.visibleViewController)
}
if let tab = base as? UITabBarController, selected = tab.selectedViewController {
return topViewController(selected)
}
if let presented = base?.presentedViewController {
return topViewController(presented)
}
return base
}
}
然后您的 class 将如下所示:
class ErrorReporting {
static func showMessage(title: String, msg: String) {
let alert = UIAlertController(title: title, message: msg, preferredStyle: UIAlertControllerStyle.Alert)
alert.addAction(UIAlertAction(title: "Ok", style: UIAlertActionStyle.Default, handler: nil))
UIApplication.topViewController()?.presentViewController(alert, animated: true, completion: nil)
}
}
方法必须是 static
才能调用它 ErrorReporting.showMessage
。
Swift Maksym Musiienko 的第 3 版回答如下:
extension UIApplication {
static func topViewController(base: UIViewController? = UIApplication.shared.delegate?.window??.rootViewController) -> UIViewController? {
if let nav = base as? UINavigationController {
return topViewController(base: nav.visibleViewController)
}
if let tab = base as? UITabBarController, let selected = tab.selectedViewController {
return topViewController(base: selected)
}
if let presented = base?.presentedViewController {
return topViewController(base: presented)
}
return base
}
}
我有一个主要的 class、AddFriendsController
,它运行以下代码行:
ErrorReporting.showMessage("Error", msg: "Could not add student to storage.")
然后我有这个 ErrorReporting.swift
文件:
导入基金会
class ErrorReporting {
func showMessage(title: String, msg: String) {
let alert = UIAlertController(title: title, message: msg, preferredStyle: UIAlertControllerStyle.Alert)
alert.addAction(UIAlertAction(title: "Ok", style: UIAlertActionStyle.Default, handler: nil))
self.presentViewController(alert, animated: true, completion: nil)
}
}
显然,self
在这里不起作用,并且给我一个错误。我如何引用当前打开的视图控制器(即在这种情况下 AddFriendsController
),因为我希望在许多不同的 swift 文件中使用相同的方法?
谢谢。
实际上,在我看来,视图控制器呈现操作应该在 UIViewController
实例上完成,而不是在模型 class.
一个简单的解决方法是将 UIViewController
实例作为参数传递
class ErrorReporting {
func showMessage(title: String, msg: String, `on` controller: UIViewController) {
let alert = UIAlertController(title: title, message: msg, preferredStyle: UIAlertControllerStyle.Alert)
alert.addAction(UIAlertAction(title: "Ok", style: UIAlertActionStyle.Default, handler: nil))
controller.presentViewController(alert, animated: true, completion: nil)
}
}
然后像下面这样称呼它
ErrorReporting.showMessage("Error", msg: "Could not add student to storage.", on: self)
您可以为 UIApplication 创建扩展方法(例如),它将 return 您的 topViewController:
extension UIApplication {
static func topViewController(base: UIViewController? = UIApplication.sharedApplication().delegate?.window??.rootViewController) -> UIViewController? {
if let nav = base as? UINavigationController {
return topViewController(nav.visibleViewController)
}
if let tab = base as? UITabBarController, selected = tab.selectedViewController {
return topViewController(selected)
}
if let presented = base?.presentedViewController {
return topViewController(presented)
}
return base
}
}
然后您的 class 将如下所示:
class ErrorReporting {
static func showMessage(title: String, msg: String) {
let alert = UIAlertController(title: title, message: msg, preferredStyle: UIAlertControllerStyle.Alert)
alert.addAction(UIAlertAction(title: "Ok", style: UIAlertActionStyle.Default, handler: nil))
UIApplication.topViewController()?.presentViewController(alert, animated: true, completion: nil)
}
}
方法必须是 static
才能调用它 ErrorReporting.showMessage
。
Swift Maksym Musiienko 的第 3 版回答如下:
extension UIApplication {
static func topViewController(base: UIViewController? = UIApplication.shared.delegate?.window??.rootViewController) -> UIViewController? {
if let nav = base as? UINavigationController {
return topViewController(base: nav.visibleViewController)
}
if let tab = base as? UITabBarController, let selected = tab.selectedViewController {
return topViewController(base: selected)
}
if let presented = base?.presentedViewController {
return topViewController(base: presented)
}
return base
}
}