Swift学习笔记笔记（一）Swift编程步骤数据类型

一、实验目的：

掌握Swift编程方法。
掌握Swift数据类型。

二、实验原理：

playground的界面与使用方法。
常量与变量的定义方法。
3.常量与变量的类型声明方法。

三、实验步骤及内容：

1. 常量与变量

// 常量的定义
let lengthOfTelephoneNumber = 8
let lengthOfIdentityCardNumber = 18
let lengthOfZipNumber = 6
//变量的定义
var totalVisits = 2000000
var numberOfMembers = 10000
var currentSpeed = 120
//常量，变量命名
var a_b = “a and b”
var aPerson = “one person”
let hello = “say hello”
let mul = “multiply operator”
var numOfApple = 88
//可读性强的命名
var numberOfStudents = 68
var idCardNumber = “320602201612120652”
let pi = 3.141516
//可读性弱的命名
var a = 68
var b = “320602201612120652”
let c = 3.141516
//类型声明
let name ： String = ““
var age ： Int = 0
//定义变量
var a_b = “a and b”
var aPerson = “one person”
var hello = “say hello”
//分配变量值
hello = “say hi”
a_b = “c and d”
//输出
print（a_b)
print（hello)
print（“The value of variable a_b is \（a_b)”)
print（aPerson)
//分隔符
var a_b = “a and b”, aPerson = “one person”, hello = “say hello”
let thisYear = “2022”
let myOrganisation = “QingChuan”
let myhobby = “Reading”
//练习题1
/*the reference code for exercisechapter： constant and variableAuthor： Morre PaulOrganisation： QingChuanDate： 2021-8-9*/
//definition part
var radius ： Double = 3.0
let pi ： Double = 3.1415
var areaOfCircle ： Double = pi * radius * radius
//output part
print（“radius = \（radius), pi = \（pi), so the area of circle is ： \（areaOfCircle)”)

2. 整型和浮点型

let minValue = Int8.min
let maxOfInt8 = Int8.max
let maxOfInt16 = Int16.max
let maxOfInt32 = Int32.max
let maxOfInt64 = Int64.max
let num1：Int8 = -128
let num2：UInt16 = 65535
let num3： Int32 = -100_0000
//整型混合运算
let result = Int（num1) + Int（num2) + Int（num3)
//32位
let fNum1： Float = 3.1415
//64位
let dNum2： Double = 3.1415926
//浮点型混合元算
let sum = Double（fNum1) + dNum2
//越界赋值
let outBoundNum1 ： UInt8 = -16
let outBoundNum2 ： Int8 = 160
//越界运算
let outBoundNum1 ： UInt8 = 16
let outBoundNum2 ： Int8 = 120
let sum = Int8（outBoundNum1) + outBoundNum2
//练习题2
let maxOfInt32 = UInt32.max
let minOfUInt = UInt.min
let intNum： Int = 10000
let doubleNum： Double = -33.66
let sumInt = intNum + Int（doubleNum)
let sumDouble = Double（intNum) + doubleNum
let correctValue1 = 200
let correctValue2 ： UInt8 = 200
//let correctValue3 ： Int8 = 200
let value1 ： Int16 = 20000
let value2 ： Int8 = 10
//let multiResult = value1 * Int16（value2)
let multiResult = Int（value1) * Int（value2)

3. 浮点型

var daylight ： Bool = true
var lightSwitch = false
if daylight {lightSwitch = falseprint（“It is daytime, so turn  light switch off!”)
} else {lightSwitch = trueprint（“It is night, please turn light switch on!”)
}
//练习题3
var isWeekend ： Bool = false
if isWeekend {print（“Today may be Saturday or Sunday.”)
} else {print（“Today is not Saturday or Sunday.”)
}
var sunnyDay = true
if sunnyDay {print（“It's sunny.”)
} else {print（“It's rainy or cloudy.”)
}

4.元组

//定义元组
let http404Error = （404, “Not Found”)
//元组赋值
let （Code, Description) = http404Error
print（Code)
print（Description)
//访问元组
print（http404Error.0)
print（http404Error.1)
let http406Error = （Code： 406, Description： “Not Acceptable”)
print（http406Error.Code)
print（http406Error.Description)
let rectangle = （len：10 , width：5)
print（rectangle.0)
print（rectangle.width)
print（rectangle)
//练习题4
//定义元组
let studentInfo = （60115, “Liang Zhang”, true)
//访问元组方法1
let （idNum, name, mCCP) = studentInfo
print（“Student \（name)'s identification number is \（idNum)”)
if mCCP {print（“\（name) is a member of Chinese Communist Party”)
} else {print（“\（name) isn't a member of Chinese Communist Party”)
}
//访问元组方法2
print（“Student \（studentInfo.1)'s identification number is \（studentInfo.0)”)
if studentInfo.2 {print（“\（studentInfo.1) is a member of Chinese Communist Party”)
} else {print（“\（studentInfo.1) isn't a member of Chinese Communist Party”)
}
//访问元组方法3
let anotherStudentInfo = （idNum： 60115, name： “Liang Zhang”, mCCP： true)
print（“Student \（anotherStudentInfo.name)'s identification number is \（anotherStudentInfo.idNum)”)
if anotherStudentInfo.mCCP {print（“\（anotherStudentInfo.name) is a member of Chinese Communist Party”)
} else {print（“\（anotherStudentInfo.name) isn't a member of Chinese Communist Party”)
}
//定义元组
let studentInfo = （60115, “Liang Zhang”, true)
//访问元组方法1
let （idNum, name, mCCP) = studentInfo
print（“Student \（name)'s identification number is \（idNum)”)
if mCCP {print（“\（name) is a member of Chinese Communist Party”)
} else {print（“\（name) isn't a member of Chinese Communist Party”)
}
//访问元组方法2
print（“Student \（studentInfo.1)'s identification number is \（studentInfo.0)”)
if studentInfo.2 {print（“\（studentInfo.1) is a member of Chinese Communist Party”)
} else {print（“\（studentInfo.1) isn't a member of Chinese Communist Party”)
}
//访问元组方法3
let anotherStudentInfo = （idNum： 60115, name： “Liang Zhang”, mCCP： true)
print（“Student \（anotherStudentInfo.name)'s identification number is \（anotherStudentInfo.idNum)”)
if anotherStudentInfo.mCCP {print（“\（anotherStudentInfo.name) is a member of Chinese Communist Party”)
} else {print（“\（anotherStudentInfo.name) isn't a member of Chinese Communist Party”)
}

5.可选型

//Swift的空值
var studentInSwift： （name： String, idNumber： String, age： Int, reward： String?) = （“Jim”, “37060116”, 19, “Best Student”)
//case 2nd： Tom has no reward
studentInSwift = （“Tom”, “37060115”, 20, nil)
//定义可选类型
var reward： String?
reward = “Best Student”
var bonus： String = “default value”
//字符串拆包
bonus = reward!
//print（“\（bonus)”)
if reward != nil {bonus = reward!print（“\（bonus)”)
} else {print（“reward is nil”)
}
var reward： String?
//可选型绑定
if let reward = reward {print（“The optional's value is \（reward)”)
} else {print（“The optional is nil”)
}
var countsOfReward： Int?
countsOfReward = 9
//可选型绑定
if let countsOfReward = countsOfReward {print（“Counts of reward is \（countsOfReward)”)
} else {print（“There is no reward record”)
}
var reward： String?
var countsOfReward： Int?
reward = “Best Student”
countsOfReward = 9
//多个可选型绑定
if let reward = reward, let countsOfReward = countsOfReward, countsOfReward > 3 {print（“reward is \（reward), counts are \（countsOfReward)”)
} else {print（“no reward or no counts or counts<=3”)
}
// nil聚合运算
var reward： String?
var countsOfReward： Int?
reward = “Best Student”
countsOfReward = nil
var valueOfReward = reward ?? “No Reward”
var valueOfCounts = countsOfReward ?? 0
print（valueOfReward)
print（valueOfCounts)
//练习题5-1
var myHobby： String?
//I like playing soccer
myHobby = “playing soccer”
//I haven't any hobby
myHobby = nil
let parsedInt = Int（“10”)
//parse a string into a int
var parseStringToInt = Int（“10”)
parseStringToInt = Int（“Picasso”)
//练习题5-2
//student's information
var name： String = “Tommy”
var hobby： String?
//force unwrapping
if hobby != nil {print（“\（name)'s hobby is \（hobby!)”)
} else {print（“\（name) has no hobby”)
}
var membership： String?
membership = “IEEE senior member”
//optional binding
if let membership = membership {print（“\（name) is \（membership)”)
} else {print（“\（name) doesn't join any orgnization!”)
}
hobby = “soccer”
//multiple optional binding
if let hobby = hobby, let membership = membership {print（“\（name)'s hobby is \（hobby) and is also \（membership)”)
} else {print（“\（name) has no hobby or doesn't join any orgnization!”)
}
//nil coalescing
var getHobby = hobby ?? “No hobby”
var getMembership = membership ?? “No membership”
hobby = nil
membership = nil
getHobby = hobby ?? “No hobby”
getMembership = membership ?? “No membership”

四、实验结果与分析：

本次实验，主要学习了如何定义常量和变量，以及练习了swift常见数据类型的使用方法，以及如何用不同的方法定义、访问元组等等，在实验中，我主要会因为自己的粗心大意，方法使用不恰当导致运行结果出现误差，检查出错误后，基本所有的实验结果都可以正常运行出来。

五、实验总结：

Swift既是一门高级语言，又是一门低层级语言Swift可以使用map和reduce来很容易创建出自己的高级函数，Swift可以快速完成代码编写，并将他们直接编译为原生二进制可执行文件，这使得性能可以与C语言的编写的程序相媲美。Swift更令人赞叹的是，可以兼顾高低两个层级。将一个数组通过闭包表达式映射到另一个数组所编译得到的汇编码，与直接对一块连续内存进行循环所得到的结果是一致的。2. Swift是一门多范式语言可以使用 Swift来编写面向对象的代码，也可以使用不变量的值，来写纯函数程序。Swift 依然可以使用大部分Objective-C功能，包括消息发送，运行时的类型判定，以及KVO等。Swift还引入了很多Objective-C不具备的特性Swift 拥有泛型，协议，值类型以及闭包等特性，这些特性是函数式风格的很好介绍。
本次课程的学习，我主要学习了如何定义常量与变量、以及swift中常见的数据类型，让我对swift编程语言有了一个基本的认识。在罗老师的带领学习下，我越来越喜欢这IOS门课程，希望在以后的学习中，我可以越来越主动去学习了解更多的知识。本次实验，我主要的学习情况总结如下：
（1）swift 中常见的数据类型
Int 、Float、Double、Character、String
Array、Dictonary、元组类型（Tuple）、可选类型（Optional）
可以看出，数据类型的首字母都是大写的
（2）如何指定变量，常量的数据类型
在常量变量名后面加上冒号(：)和类型名称
let age:Int = 10
上面代码表示：定义了一个Int类型的变量age 初始值是10
（3）一般来说，没有必要明确指定变量，常量的类型
如果在声明常量、变量时赋了初始值 Swift 以@L_673_5@推断出这个常量、变量的类型
let age = 20
//Swift 会推断出age是Int类型因为20是个整数
（4）变量初始化
Swift严格要求变量在使用之前必须进行初始化因为Swift是强类型，而且是类型安全的语言，两个类型不一样是不能相加的等等。