From 30631e5920832c905ccb500149800153c6544367 Mon Sep 17 00:00:00 2001 From: Li Ming Date: Fri, 13 Jun 2014 16:54:39 +0800 Subject: [PATCH] lost code --- source/chapter2/18_Type_Casting.md | 18 +++++++++++++----- 1 file changed, 13 insertions(+), 5 deletions(-) diff --git a/source/chapter2/18_Type_Casting.md b/source/chapter2/18_Type_Casting.md index 4d420ea9..44729652 100644 --- a/source/chapter2/18_Type_Casting.md +++ b/source/chapter2/18_Type_Casting.md @@ -35,6 +35,14 @@ 下一个代码段定义了 `MediaItem` 的两个子类。第一个子类`Movie`，在父类（或者说基类）的基础上增加了一个 `director`（导演） 属性，和相应的初始化器。第二个类在父类的基础上增加了一个 `artist`（艺术家） 属性，和相应的初始化器： + class Movie: MediaItem { + var director: String + init(name: String, director: String) { + self.director = director + super.init(name: name) + } + } + class Song: MediaItem { var artist: String init(name: String, artist: String) { @@ -47,11 +55,11 @@ ，包含两个`Movie`实例和三个`Song`实例。`library`的类型是在它被初始化时根据它数组中所包含的内容推断来的。Swift 的类型检测器能够演绎出`Movie` 和 `Song` 有共同的父类 `MediaItem` ，所以它推断出 `MediaItem[]` 类作为 `library` 的类型。 let library = [ - Movie(name: "Casablanca", director: "Michael Curtiz"), - Song(name: "Blue Suede Shoes", artist: "Elvis Presley"), - Movie(name: "Citizen Kane", director: "Orson Welles"), - Song(name: "The One And Only", artist: "Chesney Hawkes"), - Song(name: "Never Gonna Give You Up", artist: "Rick Astley") + Movie(name: "Casablanca", director: "Michael Curtiz"), + Song(name: "Blue Suede Shoes", artist: "Elvis Presley"), + Movie(name: "Citizen Kane", director: "Orson Welles"), + Song(name: "The One And Only", artist: "Chesney Hawkes"), + Song(name: "Never Gonna Give You Up", artist: "Rick Astley") ] // the type of "library" is inferred to be MediaItem[]