Switch入门第一讲

import Foundation

//常量
let age = 10
print(age)
//变量
var height = 170.3
print(height)
//类型标注
var weight: Double = 75.0

//命名规则 ：swift里不再遵循传统的命名规则，但是变量名不能有运算符，不能以数组开头
var 东东 = "东东"
print(东东)

var 🐶 = "🐱"
print(🐶)

//基本数据类型：正数类型 Int8/16/32/64 UInt8/16/32/64
//小数类型 Double,Float

print(Int8.max)
print(Int64.max)
//int 默认 64

var intValue1: Int32 = 32
var intValue2: Int64 = 64
//swift是一门类型非常安全的语言,不同的数据类型不能相互运算
var intValue3 = Int64(intValue1) + intValue2
print(intValue3)

//Bool类型

var boolValue:Bool = true
if boolValue
{
    print(true)
}
else
{
    print(false)
}

//字符,字符串
var charValue: Character = "c"
var charValue1: Character = "张"

var stringValue: String = "李四"

//字符串拼接
var stringValue1: String = "我的"
var stringValue2: String = "滑板鞋"
var stringValue3 = stringValue1 + stringValue2
print(stringValue3)

//www.baidu/9.com
var str1 = "www"
var str2 = "baidu"
var str3 = "com"
var str4 = str1 + "." + str2 + "/9." + str3
print(str4)

var str5 = "\(str1).\(str2)/9.\(str3)"
print(str5)

//字符串比较
var str6 = "apple"
var str7 = "bpple"
if str6 > str7
{
    print(str6)
}
else
{
    print(str7)
}

//字符串前后缀
//判断前缀
var str8 = "www.baidu.com"
if str8.hasPrefix("www")
{
    print(true)
}
else
{
    print(false)
}
//判断后缀
if str8.hasSuffix("com")
{
    print(true)
}
else
{
    print(false)
}

//字符大小写转换
var strr1 = "ABCD"
var strr2 = "efg"
//转为小写
print(strr1.lowercaseString)
//转为大写
print(strr2.uppercaseString)

// 可选类型,隐式解析可选类型
// "?" 可选类型:有值,没值(nil)
var intNumber: Int? = 12
print(intNumber)

// "!"强制解析 (比较危险,如果可选类型没值,就会崩溃)
var intNumber1 = intNumber!
print(intNumber1)

// 类型绑定 (比较安全,没值不走,有值走)
if let intNumber2 = intNumber
{
    print(intNumber2)
}

// "!"隐式解析可选类型(有值,没值)
// 不需要强制解析,但是,如果没值,对其操作也会崩溃
var intNum: Int64!// = 15
//print(intNum)

//可选绑定
if let intNum1 = intNum
{
    print(intNum1)
}

//数字运算 + - * / 
var intValue11 = 10
var intValue12 = 20
var intValue13 = intValue11 + intValue12
print(intValue13)

//赋值运算符 = += -= /=
intValue13 += intValue11
print(intValue13)

//关系运算符  ==  >  <  !=
var boolValue11: Bool = 5 > 4
if  boolValue11 == true
{
    print(true)
}
else
{
    print(false)
}

// 三目运算符
var intValue111: Int  = 2 > 3 ? 2 : 3
print(intValue111)

// 逻辑运算符 ! && ||
var girlAge = 30
var girlHeight: Double = 180.0
if girlAge >= 30 && girlHeight >= 180.0
{
    print("同意结婚")
}
else
{
    print("女方要求没达到,不同意")
}

// 闭区间,半闭区间运算符
// 闭区间
var rangeValue: Range = 1...6
print(rangeValue)
//半闭区间
var rangValue1: Range = 1..<7
print(rangeValue)
for var a in rangValue1
{
    print(a)
}

//循环语句,分支语句
var sum = 0
for var i = 0; i < 101; i++
{
    sum = sum + i
}
print(sum)

//while 循环
var sum1 = 0
var i = 0
while i <= 100
{
    sum1 += i
    i++
}
print(sum1)

//do while
var sum2 = 0
i = 0
repeat
{
    sum2 += i
    i++
}
while i <= 100
print(sum2)

// if  else
var score = 70
if score >= 90
{
    print("优秀")
}
else if score >= 80
{
    print("良好")
}
else if score >= 60
{
    print("及格")
}
else
{
    print("不及格")
}


// switch
switch score
{
case 90...100:
    print("优秀")
case 80..<90:
    print("良好")
case 60..<80:
    print("及格")
default:
    print("不及格")
}