RW Closures Section

challenges1.swift

//: ## Episode 08: Closures & Collections

// --------------------------------------
class Student {
  let name: String
  var grade: Int
  var pet: String?
  var libraryBooks: [String]
  
  init(name: String, grade: Int, pet: String? = nil, libraryBooks: [String]) {
    self.name = name
    self.grade = grade
    self.pet = pet
    self.libraryBooks = libraryBooks
  }
  
  func getPassStatus(lowestPass: Int = 50) -> Bool {
    grade >= lowestPass
  }
  
  func earnExtraCredit() {
    grade += 10
  }
}

let chris = Student(name: "Chris", grade: 49, pet: "Mango", libraryBooks: ["The Book of Atrus", "Living by the Code", "Mastering Git"])
let sam = Student(name: "Sam", grade: 99, pet: nil, libraryBooks: ["Mastering Git"])
let catie = Student(name: "Catie", grade: 75, pet: "Ozma", libraryBooks: ["Hogfather", "Good Omens"])
let andrea = Student(name: "Andrea", grade: 88, pet: "Kitten", libraryBooks: ["Dare to Lead", "The Warrior's Apprentice"])

let students = [chris, sam, catie, andrea]
// --------------------------------------

/*:
 ## Challenge 1 - `forEach` & `map`
 There are two `for` loops below.
 Rewrite one of them using `forEach` and the other with `map`
*/

//for student in students {
//  student.earnExtraCredit()
//}

students.forEach { $0.earnExtraCredit() }

//var classLibraryBooks: [[String]] = []
//for student in students {
//  classLibraryBooks.append(student.libraryBooks)


let classBooks = students.map { $0.libraryBooks }

//let classBooks2: [String] = students.map {
//    $0.libraryBooks.forEach(){ $0 }
//}


let bookList = classBooks.map { (books) in
    print(books)
}


/*:
 ## Challenge 2 - compactMap
 Replace the `for` loop below with compactMap.
 It will filter out the `nil` values for you!
*/

var classPets: [String] = []
for student in students {
  if let pet = student.pet {
    classPets.append(pet)
  }
}

let validPets = students.compactMap { s in
    s.pet
}

let validPets2 = students.compactMap { $0.pet }

print(validPets, validPets2)

/*:
 ## Challenge 3 - flatMap
 In Challenge 1 you created `libraryBooks`, an array of String arrays!
 Try using flatMap to flatten all of the books into a single String array.
*/

let flatBooks: [String] = classBooks.flatMap { $0 }
print(flatBooks)

let flatBooks2: [String] = classBooks.flatMap { $0 }
print(flatBooks2)

let flatBooks3: Set = Set(classBooks.flatMap { $0 }.sorted())
print(flatBooks3)

let flatBooks4: Set = Set(classBooks.flatMap { $0 }.sorted(by: >))
print(flatBooks4)

let flatBooks5: Set = Set(classBooks.flatMap { $0 }.sorted(by: <))
print(flatBooks5)

print(flatBooks5.sorted())
print(flatBooks5.sorted(by: >))
print(flatBooks5.sorted(by: <))

//THIS IS THE BEST!!!
let classBooksFlat = Set(students.flatMap { $0.libraryBooks }).sorted()
print(classBooksFlat)

challenges2.swift

//: [⇐ Previous: 09 - filter, reduce, and sort](@previous)
//: ## Episode 10: Challenge - filter, reduce, and sort

/*:
 ## Challenge Time 😎
 
 Create a constant array called `names` which contains some names as strings (any names will do — make sure there’s more than three though!). Now use `reduce` to create a string which is the concatenation of each name in the array.
*/

let names = ["Bonny", "George", "Linda", "Diane"]
let namesString = names.reduce("", +)
namesString
//var namesString2 = names.reduce("My dogs are called ") { message, name -> String in
//    message += "\(name) and "
//}
//namesString2
//var namesString2 = names.reduce("My dogs are called ") { $0 += ("\($1) and ") }
//namesString2


//let array = ["Andrew", "Ben", "John", "Paul", "Peter", "Laura"]
//let joined = array.joined(separator: ", ")


/*:
 Using the same `names` array, first filter the array to contain only names which have more than four characters in them, and then create the same concatenation of names as in the above exercise. (Hint: you can chain these operations together.)
*/

let names2 = ["Bob", "Bonny", "George", "Linda", "Joe", "Diane"]
//let dwarvesAfterM = arrayOfDwarfArrays.flatMap { dwarves -> [String] in
//  dwarves.filter { $0 > "M" }
//}.sorted()

//var bothReducedAndFiltered = names.filter { $0.count > 5 }.reduce("", +)
//print(bothReducedAndFiltered)

var bFandR = names2.filter { (name) -> Bool in
    name.count > 3
}.reduce("My pets are called ") { (message, name) -> String in
    message + " and " + name
}
print(bFandR)

var bothReducedAndFiltered2 = names2.filter { $0.count > 3 }.joined(separator: " and ")
print(bothReducedAndFiltered2)
/*:
 Create a constant dictionary called `namesAndAges` which contains some names as strings mapped to ages as integers. Now use `filter` to create a dictionary containing only people under the age of 18.
*/

let namesAndAges = ["Bob": 12, "Bonny": 43, "George": 29, "Linda": 10, "Joe": 16, "Diane": 92]

//var youths = namesAndAges.filter { (name, age) -> Bool in
//    age < 18
//}

//var youths = namesAndAges.filter { $1 < 18 }

//good balance between clear and succint.
var youths = namesAndAges.filter { (_, age) in age < 18 }
print(youths)

var youths2 = namesAndAges.filter { $0.value < 18 }
print(youths2)

//interesting that the order is different.


/*:
 Using the same `namesAndAges` dictionary, filter out the adults (those 18 or older) and then use `map` to convert to an array containing just the names (i.e. drop the ages).
*/

let adultNames = namesAndAges.filter { $0.value >= 18 }.map { $0.key }

print(adultNames)

let adultNames2 = namesAndAges.filter { (_, age) in age >= 18 }.map { (name, _) in name }//.sorted()
print(adultNames2)

//: [⇒ Next: 11 - Conclusion](@next)