dineshba

let fanNames = computerLab.laptops
    .filter({laptop in !laptop.name.contains("Mac") })
    .filter({laptop in laptop.fan != nil})
    .map({laptop in laptop.fan!.name})

// Simplified
let fanNames = computerLab.laptops
    .filter({laptop in !laptop.name.contains("Mac") })
    .compactMap({laptop in laptop.fan?.name})  //compactMap will filter out nil values by default

dineshba

struct ComputerLab { // Computer Lab contains list of laptops.
    let laptops: [Laptop]
}
// we want to get the list of mac laptops

// Traditional way
var macLaptops: [Laptop] = []
for laptop in computerLab.laptops {
    if laptop.name.contains("Mac") {
        macLaptops.append(laptop)

dineshba

if case .sugar = sugarcane.taste {              // if sugarcane.taste is `.sugar` then 
    print("yummmmy sugarcane")                  // enters into if
}
if case .salty(let value) = frenchFries.taste { // frenchFries.taste is .salty(10), so it matches
    if value < 10 {                             // the case and assign the value 10 to `value`
        print("manageable")                     // we can use the `value` inside the `if case`
    } else {
        print("impossible")
    }
}

dineshba

func printSummary(_ programmer: Programmer) {
    guard let laptop = programmer.laptop else {     // set the value of laptop if `programmer.laptop` is not nil 
        print("\(programmer.name) have no laptop")  // and will go line 6. If `programmer.laptop` is nil, it will
        return                                      // enter into else case and return to caller of this function.
    }
    guard let laptopFan = laptop.fan else {         // Syntax
        print("\(laptop.name) contains no fan")     // guard let constant = expression else {
        return                                      //   return returnValue
    }                                               // }
    print("\(laptop.name) contains \(laptopFan.name) fan")

dineshba

if let laptop = programmer.laptop {                  // set the value of laptop if `programmer.laptop` is not nil and
                                                     // enter into if-case or enter into `else` case.
    if let laptopFan = laptop.fan {                  // set the value of laptopFanName if `laptop.fan` is not nil and
                                                     // enter into if-case or enter into `else` case.
        print("\(laptop.name) contains \(laptopFan.name) fan")
    } else {
        print("\(laptop.name) contains no fan")       // Note: String interpolation "\(value)"
    }
} else {
    print("\(programmer.name) have no laptop")

dineshba

extension Double { //swift class
    func half() -> Double {
       return self / 2
    }
}

1.3.half()          //0.6500000000000000
1000.0.half()       // 500
Double(999).half()  // 499.5

dineshba

struct Square {
  let size: Int
  
  var area: Int {        // var computedProperty: ReturnType {
    return size * size   // return (compute from other instance variables)
  }                      // }

  var perimeter: Int {
    return 4 * size
  }

dineshba

// mandatory argument names for caller
func add(augend: Int, addend: Int) -> Int {
  return augend + addend
}
let sum = add(augend: 5, addend: 2)

// no argument names for caller (underscore for no name)
func add(_ augend: Int, _ addend: Int) -> Int {
  return augend + addend
}

dineshba

let a = 5 // Int
let b = 5.0 // Double
let c = Float(5.3) // Float
let sugar = Sugar(taste: .sweet) // Sugar
let sweet = Taste.sweet // Taste
let sour: Taste = .sour // Taste
let sum = sum(5, nil) // Int?
let firstValue = [1,2,3].first // Int?

dineshba

struct Programmer {
  let brain: Brain
  let laptop: Laptop?
  let name: String
}
struct Brain {
}
struct Laptop {
  let name: String
  let fan: Fan?