Swift:switch case从字典键中复用值

Question

我想为多个值做一个切换案例,其中这些值来自字典的键.

myDict = ["dog": "waf", "cat": "meaow", "cow":"meuh"]
let animal = "cat"

switch animal {

case myDict.keys :
   print(myDict[animal])

case "lion" :
   print("too dangerous !")
}

default :
   print("unknown animal")
}

如何获取myDict键并将其转换为元组(或其他))？我试过Array(myDict.keys)但它失败了:

Expression pattern of type 'Array<String>' cannot match values of type
'String'

Answer 1

你可以通过一个where子句实现你想要的.这是怎么做的.

let myDict = ["dog": "waf", "cat": "meaow", "cow":"meuh"]
let animal = "cat"

switch animal {

case _ where myDict[animal] != nil :
    print(myDict[animal])

case "lion" :
    print("too dangerous !")

default :
    print("unknown animal")
}