print("HD: \(hd.width)x\(hd.height)")
print("Cinema: \(cinema.width)x\(cinema.height)")
+// Enumeration 也是值类型
+enum CompassPoint: String {
+ case North
+ case South
+ case East
+ case West
+}
+
+var originDirection = CompassPoint.East
+var currentDirection = originDirection
+currentDirection = .West
+print("originDirection: \(originDirection) currentDirection: \(currentDirection)")
+
class VideoMode {
var resolution = Resolution()
if someVideoMode !== tenEighty {
print("someVideoMode & tenEighty refer to different VideoMode instance")
-}
\ No newline at end of file
+}
// lazy 属性在声明前加上 lazy 关键字
// 如果一个被标记为 lazy 的属性在没有初始化时就同时被多个线程访问，则无法保证该属性只会被初始化一次
+class DataImporter {
+ var name: String = ""
+ init() {
+ self.name = "DataImporter"
+ print("...\(self.name)...")
+ }
+}
+
+class DataManager {
+ lazy var importer = DataImporter()
+ var data: Array<String> = []
+}
+
+let dataManager = DataManager()
+dataManager.data.append("Data_0")
+dataManager.data.append("Data_1")
+dataManager.data.append("Data_2")
+// lazy 变量还未初始化
+print("the DataImporter instance for the importer property has not yet been created")
+
+// 主动调用才初始化
+dataManager.importer
+
+
printLine("Computed Properties")
}
let fourByFiveByTwo = Cuboid(width:4.0, height:5.0, depth:2.0)
-print(fourByFiveByTwo.volume)
\ No newline at end of file
+print(fourByFiveByTwo.volume)