Swift:Errors thrown from here are not handled because the enclosing catch is not exhaustive
在学习Swift错误处理的时候,官方给出的do-catch例子如下:......letfavoriteSnacks=["Alice":"Chips","Bob":"Licorice","Eve":"Pretzels",]funcbuyFavoriteSnack(person:String,vendingMachine:VendingMachine)throws{letsnackName=favor