Swift_可选链

Swift_可选链

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点击查看源码

//可选链
func test() {
    class Person {
        //可选属性可能为nil或Residence类
        var residence: Residence?
    }

    class Residence {
        var numberOfRooms = 1
    }

    let john = Person()
    john.residence = Residence()

    //可选获得
    var roomCount = john.residence?.numberOfRooms

    print(roomCount)

    //强制获得
    roomCount = john.residence!.numberOfRooms

    print(roomCount)

    // if获得
    if let roomCount = john.residence?.numberOfRooms {
        print(roomCount)
    }

    /*  print

     Optional(1)
     Optional(1)
     1

     */
}