Swift 基础-2

1. 类型别名

为已有的类型取了另一个名字，方便表示

typealias dog = Int
var a: dog = 10
var b: Int = 20
print(a, b)

typealias cat = String
var c: cat = "Hello"
var d: String = "Swift"
print(c, d)

2. 类型转换

使用圆括号转换

var a = 3.14
print("a = \(a)")
print("a = " + String(a))
var b = false
print("b is " + String(b))