//: Playground - noun: a place where people can play

import Cocoa

var str1 ="供选链接和强制拆包的不同。

"

class Person {

   var residence: Residence?//供选连接

}

class Residence {

   var rooms = [Room]()

   var numberOfRooms:Int {

       return rooms.count

    }

    subscript(i:Int) ->Room {

       return rooms[i]

    }

   func printNumberOfRooms() {

        println("The number of rooms is\(numberOfRooms)")

    }

   var address: Address?

}

//假设你创建一个新的 Person实例,它的 residence属性因为是被定义为供选的,此属性将默认初始化为空:

//let john = Person()

/*

假设你想使用声明符!强制拆包获得这个人 residence属性 numberOfRooms 属性值,将会引发执行时错误,由于这时没有能够供拆包的 residence值。

*/

//let roomCount = john.residence!.numberOfRooms

//供选链接提供了一种还有一种获得 numberOfRooms的方法。利用供选链接,使用问号来取代原来!的位置:

//let roomCount = john.residence?

.numberOfRooms

/*

if let roomCount = john.residence?.numberOfRooms {

    println("john‘s residence has \(roomCount) room(s).")

} else {

    println("Unable to retrieve the of rooms.")

}

john.residence = Residence()

if let roomCount = john.residence?

.numberOfRooms {

    println("john‘s residence has \(roomCount) room(s).")

} else {

    println("Unable to retrieve the of rooms.")

}*/

/*

为供选链接定义模型类

这些类是由上面的 Person 和 Residence 模型通过加入一个 Room和一个 Address 类拓展来。

*/

class Room {

   let name: String

   init(name: String) {

       self.name = name

    }

}

class Address {

   var buildingName:String?

   var buildingNubmer:String?

   var street: String?

   func buildingIdentifier() ->String? {

       if (buildingName !=nil) {

           return buildingName

        }else if (buildingNubmer != nil) {

            returnbuildingNubmer

        }else {

           return nil

        }

    }

}

//通过供选链接调用属性

let john =Person()

iflet roomCount =john.residence?.numberOfRooms {

    println("John‘s residence has\(roomCount) room(s).")

}else {

    println("Unable to retrieve the number of rooms.")

}

//通过供选链接调用方法

var uu =9

if(john.residence?.printNumberOfRooms() != nil) {

    println("It was possible to print the number of rooms.")

}else {

    println("It was not possible to print the number of rooms.")

}

//使用供选链接调用角标

iflet firstRoomName =john.residence?[0].name {

    println("The first room name is\(firstRoomName).")

}else {

    println("Unable to retrieve the first room name.")

}