Swift可选链

//可选链测试

class Person{

var residence:Residence!

var name:String

init(name:String){

self.name = name

}

}

///住宅

class Residence {

var residenceNum = 101

}

var lucy = Person(name: "Lucy")

//没有为lucy初始化住宅

if let roomNumber1 = lucy.residence?.residenceNum {

print("\(lucy.name)有住宅,住宅号是\(roomNumber1)")

}else{

print("\(lucy.name)没有住宅")

}

var lily = Person(name: "Lily")

lily.residence = Residence()

if let roomNumber2 = lily.residence?.residenceNum {

print("\(lily.name)有住宅,住宅号是\(roomNumber2)")

}else{

print("\(lily.name)没有住宅")

}