如何在Swift模式匹配元组时解开一个Optional？

在Swift中，有一个常用的用于解开option的if let模式：

 if let value = optional { print("value is now unwrapped: \(value)") } 

我目前正在做这种模式匹配，但在元组切换的情况下，这两个参数是可选项：

 //url is optional here switch (year, url) { case (1990...2015, let unwrappedUrl): print("Current year is \(year), go to: \(unwrappedUrl)") } 

但是，这打印：

 "Current year is 2000, go to Optional(www.google.com)" 

有没有办法，我可以解开我的可选模式匹配只有当它不是零？ 目前我的解决方法是这样的：

 switch (year, url) { case (1990...2015, let unwrappedUrl) where unwrappedUrl != nil: print("Current year is \(year), go to: \(unwrappedUrl!)") } 

Answer 1

你可以使用x? 模式：

 case (1990...2015, let unwrappedUrl?): print("Current year is \(year), go to: \(unwrappedUrl)") 

x? 只是.some(x)一个快捷方式，所以这相当于

 case (1990...2015, let .some(unwrappedUrl)): print("Current year is \(year), go to: \(unwrappedUrl)") 

Answer 2

你可以这样做：

 switch(year, x) { case (1990...2015,.Some): print("Current year is \(year), go to: \(x!)") } 

你也可以做

  switch(year, x) { case (1990...2015, let .Some(unwrappedUrl)): print("Current year is \(year), go to: \(unwrappedUrl)") }