Swift Basics

LearnSwift.swift

// variable and constant
var a = 10 // variable can be updated later
let PI = 3.14 // can not modify later

// Data types (Int, Float, Bool, Double, String) or Type Annotations
var age: Int = 10
var name:String = "John"
var radius: Float = 2.5
var area: Double = 14.50
var isAlive: Bool = false

// joining strings
var name = "Smith"
var age = 30
var userInfo = "User name is \(name) and his age is \(age)"
print(userInfo)

// if - else
if age > 18 {
    print("\(name) can vote")
}else {
    print("\(name) can not vote")
}

//switch statement
var dayOfWeek: Int = 3
switch dayOfWeek {
case 1,2,3,4,5,6,7:
   print("It is a week day")
default:
    print("Wrong input : it's not a week day ")
}

// ternary operator
var canVote = age >= 18 ? true : false
print("You can vote : \(canVote)")


// for loop
var sum:Int = 0
for index in 1...5 {
   sum += index
}
print("sum of 1 to 5 is ", sum)


// while loop
var tableNo = 2
var counter = 1
while(counter <= 10) {
    print(tableNo , "*", counter, "=", counter * tableNo)
    counter+=1
}

// repeat loop
tableNo = 2
counter = 1
repeat {
    print(tableNo , "*", counter, "=", counter * tableNo)
    counter+=1
} while(counter <= 10)


// functions
func greetings() {
    print("Hello Sir/Madam")
}

// passing parameters
func greetingUser(user:String) {
    print("Hello, ",user)
}

// return values
func addTwoNUmbers(num1: Int, num2: Int) -> Int {
    return num1 + num2
}

//greetings()
greetingUser(user: "John")
print("Func Add 2 numbers ", addTwoNUmbers(num1: 10, num2: 20))

// return multiple values
func getUser() -> (firstName: String, lastName: String) {
    (firstName: "Tom", lastName:"Cruise")
}

let user = getUser()
print("User \(user.firstName) last name is : \(user.lastName)")

let (firstName, _) = getUser()
print("User \(firstName)")


// class
class BlogPost {
    var title:String? = nil;
    var body:String? = nil;
    var author:String? = nil;
    var publishDate:String? = nil;
}

var b = BlogPost()
print(b.title ?? "No title found")
b.title = "Swift for beginners"
print(b.title ?? "No title found")

// inheritance
class Laptop {
    var weight: Float = 2.8
    var color : String = "Black"

    func bootSpeed() {
        print("Old Laptop take 15 seconds in booting")
    }
}

class MacBook : Laptop {
    override func bootSpeed() {
        //super.bootSpeed()
        print("New M1 chip can boot in 3-4 seconds")
    }

}

var oldLaptop = Laptop()
oldLaptop.bootSpeed()

var m1MackBook = MacBook()
print("Macbook color is \(m1MackBook.color)")
m1MackBook.bootSpeed()


// initializers and optionals
class Person {

    var name:String?
    var age:Int?
    var behaviour: String?

//    init() {
//        print("called init method")
//        name = "John"
//        age = 30
//    }
    init(_ name:String, _ age:Int) {
        self.name = name
        self.age = age
    }

    convenience init(behaviour: String){
        self.init("Max", 24)
        self.behaviour = behaviour
    }
}

var a1 = Person("John", 30)
a1.name
a1.age
a1.behaviour

var b1: Person?
b1 = a1
b1?.age
a1.age = 35
b1?.age = 40
a1.age

if let canVote = a1.age {
    if(canVote > 18){
        print("Yes you can vote")
    }else{
        print("No you can not vote")
    }
}

var hasIdentity: Bool {
    return a1.name != nil
}

print("user a has idendity \(hasIdentity)")

if let aBehaviour = a1.behaviour {
    print("A's Behaviour \(aBehaviour)")
}else {
    print("A has no Behaviour")
}

let c = Person(behaviour: "is a Good Person")
print("C ", c.behaviour ?? "has no behaviour")
print("C name is \(c.name ?? "") and age is \(c.age ?? 0 )")


// Array
var employeeArray = ["John", "Max", "Nick"]
// other way is => var employeeArray = [String]()
print(employeeArray)
print("Total Employees \(employeeArray.count)")
print("access 0th index -> \(employeeArray[0])")

// traverse
for employee in employeeArray {
    print(employee)
}

employeeArray[0] = "Kumaar"
print(employeeArray)

// Dictionaries (Collection for key-value pair)
var employeesDict = ["name": "John", "Job":"Swift Developer"]
print(employeesDict["name"]!)
print(employeesDict.popFirst()!)

var countries = Dictionary<String, String>()
//var countries = [String:String]()
countries["IN"] = "India"
countries["US"] = "America"

for (code, country) in countries {
    print("Country Code : \(code) - \(country)")
}

// Sets (collection with no order and no duplicates values)
var numbers = Set([1,2,2,1,3,7,6,5,3])
print(numbers)

// Enum
enum weekDays { case Monday, Tuesday, Wednesday, Thursday, Friday, Saturday , Sunday}
var day = weekDays.Monday
day = .Friday
print(day)
print(weekDays.Monday)

// Handling errors
enum EmailError : Error {
    case invalid
}

func checkEmail(_ email:String!) throws -> String {
    
    if(email == nil) {
        throw EmailError.invalid
    }
    
    if(!email.contains("@")){
        throw EmailError.invalid
    }
    
    return "Valid Email"
}

do {
    let result = try checkEmail("abc")
    print(result)
}catch EmailError.invalid {
   print("Not a valid email")
}catch {
    print("wrong input")
}

// Closures
let oddEvenNumbers = [1,2,3,4,5,6,7,8,9]
let onlyOdd = oddEvenNumbers.filter({ (item : Int ) -> Bool in
    return item % 2 != 0
})
print(onlyOdd)

// short operation with closures
let onlyEven = oddEvenNumbers.filter { $0 % 2 == 0 }
print(onlyEven)


// In Swift, structs are value types whereas classes are reference types. When you copy a struct, you end up with two unique // copies of the data. When you copy a class, you end up with two references to one instance of the data. It's a crucial  // // difference, and it affects your choice between classes or structs.

// Structs
struct Car {
    var color : String
    var speed : Int
    var gear: Int = 4 // default value
    var onSale : Bool = true
    
    // if you want to update struct value, use mutating
    mutating func stopSales() {
        onSale = false
    }
}

var carA = Car(color: "Red", speed: 180, gear: 5)
var carB = Car(color: "Grey", speed: 100)

print(carA)
print(carB)



// Property Observers
struct Weather {
    var temperature = 0 {
        didSet {
            print("temperature is now \(temperature) degree")
        }
    }
}

var weather = Weather()
weather.temperature += 15
weather.temperature -= 10

// Access Modifiers & static properties
struct Student {
    static let className = "First Standard"
    private(set) var name : String
    private(set) var grade: String
        
    mutating func updateGrade(newGrade : String) {
        self.grade = newGrade
    }
}

var st = Student(name: "John", grade: "A")
st.updateGrade(newGrade: "A+")
// st.name = "Smith" // not allowed for private members
Student.className
print(st)

// Protocols
protocol Person {
    
    var name: String { get }
    var age: Int { get set }
    
    func PersonHabbits(for habbits: String) -> String
}

class Male : Person {
    var age: Int = 0
    let name : String = "John"
    
    func PersonHabbits(for habbits: String) -> String {
        habbits
    }
}

var male = Male()
male.age = 24
male.PersonHabbits(for: "Watching football")



// Extensions
extension Collection {
    var isNotEmpty : Bool {
        isEmpty == false
    }
}

let games = ["Football", "Hockey", "Baseball"]
if games.isNotEmpty {
    print("Total games are \(games.count)")
}


// guard optional
func printAge(of age: Int?) {
    guard let age = age else {
        print("please provide age")
        return
    }
    
    print("Your age is \(age)")
}

printAge(of: nil)
printAge(of: 20)