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梁杰
2015-08-02 11:21:19 +08:00
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source/chapter2/17_Optional_Chaining.md
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@ -189,6 +189,12 @@ Residence中得printNumberOfRooms()方法输出当前的numberOfRooms值：
类似的，可以通过下标，用可空链式调用来赋值： 类似的，可以通过下标，用可空链式调用来赋值：
john.residence?[0] = Room(name: "Bathroom")
这次赋值同样会失败，因为`residence`目前是`nil`。
如果你创建一个Residence实例，添加一些Room实例并赋值给john.residence，那就可以通过可选链和下标来访问数组中的元素：
let johnsHouse = Residence() let johnsHouse = Residence()
johnsHouse.rooms.append(Room(name: "Living Room")) johnsHouse.rooms.append(Room(name: "Living Room"))
johnsHouse.rooms.append(Room(name: "Kitchen")) johnsHouse.rooms.append(Room(name: "Kitchen"))