Swift 基础

变量与常量

let name: String = "YC"      // 常量
var count: Int = 0            // 变量

可选值

var nickname: String? = nil
if let name = nickname {
    print(name)
}

函数

func greet(person: String, from city: String = "Beijing") -> String {
    return "Hello \(person) from \(city)"
}

协议

protocol Drawable {
    func draw()
    var area: Double { get }
}