Swift学习记录01

Swift学习记录01

1.定义常量、变量

//let定义常量,不可被修改
let constants = "constants1"
//var定义变量,可修改
var variables = "variables1"

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2.数组相关

• 定义数组

//定义一个数组,在中括号中[]指定数组元素类型,通过append()方法添加元素
var arrays = [String]()
arrays.append("test")
print(arrays)

• 元素排序

//用sorted()方法排序
let cities = ["London", "Tokyo", "Rome", "Budapest"]
print(cities.sorted())

//reversed()方法逆向排序
let presidents = ["Bush", "Obama", "Trump", "Biden"]
let reversedPresidents = presidents.reversed()
print(reversedPresidents)

• 元素删除

//remove(at:)删除指定元素,removeAll()删除所有元素
var characters = ["Lana", "Pam", "Ray", "Sterling"]
characters.remove(at: 2)
characters.removeAll()
print(characters)

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3.字典

//通过[key:value]键值对定义字典
let employee2 = ["name": "Taylor Swift", "job": "Singer",  "location": "Nashville"]
//用key取出元素,后面跟default可以在key不存在时给出一个自定义的默认值
print(employee2["name", default: "Unknown"])
print(employee2["job", default: "Unknown"])
print(employee2["location", default: "Unknown"])

• 定义空字典

//用[String: Int]()、[String: String]()这种形式可以创建空字典[key type: value type]()
var heights = [String: Int]()
//通过key给对应value赋值向字典中添加元素
heights["Yao Ming"] = 229
heights["Shaquille O'Neal"] = 216
heights["LeBron James"] = 206

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4.set集合

• 定义集合

//定义时直接添加元素
var people = Set(["Denzel Washington", "Tom Cruise", "Nicolas Cage", 
    "Samuel L Jackson"])
//定义空集合Set<TYPE>(),用insert()方法添加元素
var people = Set<String>()
people.insert("Denzel Washington")
people.insert("Tom Cruise")
people.insert("Nicolas Cage")
people.insert("Samuel L Jackson")

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5.枚举型enum

//enum后面跟名字
enum Weekday {
    case monday, tuesday, wednesday, thursday, friday
}
//定义变量第一次赋值过之后,后面可以不用再写枚举名称,直接.value
var day = Weekday.monday
day = .tuesday
day = .friday

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