Swift 系统学习 02 字符串 元组 给元组分量命名

/*

* 本节内容:

* 1.Bool

* 2.String/Character

* 3.Tuple(*****)

*/

显示和隐式声明Bool类型

let swiftIsCool: Bool = true
let swiftIsHard = false
let value = 10

哪怕只有一行语句, 必须加大括号

必须只能true/false才作为if条件; 非零值不能作为条件

if value == 10 {
    print("I think so.")
}

if swiftIsHard {
    print("I donot agree with u.")
}

显示和隐式声明字符串和字符

var stringOne = "hello swift"
var stringTwo: String = "hello world"

字符串插值(String Interpolation)

var stringThree = "Merge two string: \(stringOne) and \(stringTwo)"

字符串拼接: "+"

var stringFour: String = "Say hello to "
let stringFive = "Jonny"
let stringReslut = stringFour + stringFive

+=对于字符串来说, 两个字符串拼接好之后, 再赋值给左边变量

mutable: 可变的; NSMutableArray

stringFour += stringFive

字符串和字符的关系: 打印stringFour的所有字符

for character in stringFour.characters {
    // character是一个常量
    print("stringFour's character is \(character)")
}

字符类型必须显示声明

let oneCharacter: Character = "!"
String(oneCharacter) + stringFour

let chineseChar: Character = "周"
let emojiOne: Character = "