Day1-Day4 : Simple Data

Basic variables

Swift must always know the type of data inside a constant or variable,and mostly uses type inference to figure that out based on the data we assign. However, it’s also possible to use type annotation to force a particular type.

String

//string 中引用
let str = "This book called \"Long walk to freedom \""

//多文字换行
let str2 = """
abcdef
"""

Int

//下划线分开
let bigNumber = 100_000_000

Double

不同类型的数字之间不支持运算

Boolean

// 更换 T-F 方法
.toggle()

Array

let arr : [String] = ["1","a","apple"]

Dictionary

let dic : [String: Int] = {"name":1,"gender":2}

dic["name",default:0]

Set

let s = Set(["1","b","e"])

Enum

//raw value
enum SomeType { case type1,type2 }

//with an associated value
enum SomeTypeTwo { case someMethod(number: Int) }