Swift_01 The Basics (1)

1. 常量和变量

1.1 声明常量和变量

let maximumNumberOfLoginAttempts = 10
var currentLoginAttempt = 0
var x = 0.0, y = 0.0, z = 0.0

1.2 类型标注

var welcomeMessage: String
welcomeMessage = "Hello"var red, green, blue: Double

1.3  常量和变量命名

let π = 3.14159
let 你好 = "你好世界"
let ?? = "dogcow"

1.4 打印常量和变量

print(friendlyWelcome)