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Arrays and collections

Array

var scores = [Int]()
// array is empty: []

.count Property

var grocery = ["🥓", "🥞", "🍪", "🥛", "🍊"]
print(grocery.count)
// print: 5

Index

The index refers to the item's position in the ordered list, and a single element is retrieved from the array using the subscript syntax array[index].

var vowels = ["a", "e", "i", "o", "u"]

print(vowels[0]) // prints: a
print(vowels[1]) // prints: e
print(vowels[2]) // print: i
print(vowels[3]) // prints: o
print(vowels[4]) // prints: u

Note: Swift arrays are zero-indexed, meaning the first element has index 0.

Initialize With Array Literal

// use type inference:
var snowfall = [2.4, 3.6, 3.4, 1.8, 0.0]
// explicit type:
var temp: [Int] = [33, 31, 30, 38, 44]

Initialize With Default Value

var teams = [Int](repeating: 0, count: 3)
print(teams) // prints: [0, 0, 0]
// or with Array type
var sizes = Array<Int>(repeating: 0, count: 3)
print(sizes) // prints: [0, 0, 0]

.append() Method and += Operator

var gymBadges = ["Boulder", "Cascade"]
gymBadges.append("Thunder")
gymBadges += ["Rainbow", "Soul"]
// ["Boulder", "Cascade", "Thunder",
// "Rainbow", "Soul"]

.insert() and .remove() Methods

var moon = ["🌖", "🌗", "🌘", "🌑"]
moon.insert("🌕", at: 0)
// ["🌕", "🌖", "🌗", "🌘", "🌑"]

moon.remove(at: 4)
// ["🌕", "🌖", "🌗", "🌘"]

Iterate Over an Array

var employees = ["Peter", "Denial", "Jame"]
for person in employees {
  print(person)
}
// print: Peter
// print: Denial
// print: Jam

Collection (Set)

var paintingsInMOMA: Set = [
  "The Dream",
  "The Starry Night",
  "The False Mirror"
]

We can use a collection (Set) to store unique elements of the same data type

Empty Collection (Set)

var team = Set<String>()

print(team)
// print: []

Populate the Collection

var vowels: Set = ["a", "e", "i", "o","u"]

To create a set filled with values, use the Set keyword before the assignment operator.

.insert()

var cookieJar: Set = [
  "Chocolate Chip",
  "Oatmeal Raisin"
]
// add a new element
cookieJar.insert("Peanut Butter Chip")

.remove() and .removeAll() Methods

var oddNumbers: Set = [1, 2, 3, 5]

// remove existing element
oddNumbers.remove(2)
// remove all elements
oddNumbers.removeAll()

contains()

var names: Set = ["Rosa", "Doug", "Waldo"]
print(names.contains("Lola")) // print: false

if names.contains("Waldo"){
  print("There's Waldo!")
} else {
  print("Where's Waldo?")
}
// print: There's Waldo!

.isEmpty Property

var emptyList = [String]()
print(emptyList.isEmpty)     // print: true

var populatedList: [Int] = [1, 2, 3]
print(populatedList.isEmpty) // print: false

Iterate Over a Collection

var recipe: Set = ["Egg", "Flour", "Sugar"]

for ingredient in recipe {
  print ("Include \(ingredient) in the recipe")
}

.isEmpty Property

var emptySet = Set<String>()
print(emptySet.isEmpty)     // print: true

var populatedSet: Set = [1, 2, 3]
print(populatedSet.isEmpty) // print: false

.count Property

var band: Set = ["Peter", "Denial", "Jame"]

print("The band has \(band.count) players.")
// print: Band has 4 players.

.intersection() Intersection

var setA: Set = ["A", "B", "C", "D"]
var setB: Set = ["C", "D", "E", "F"]

var setC = setA.intersection(setB)
print(setC) // print: ["D", "C"]

.union()

var setA: Set = ["A", "B", "C", "D"]
var setB: Set = ["C", "D", "E", "F"]

var setC = setA.union(setB)
print(setC)
// print: ["B", "A", "D", "F", "C", "E"]

.symmetricDifference() Symmetric Difference

var setA: Set = ["A", "B", "C", "D"]
var setB: Set = ["C", "D", "E", "F"]

var setC = setA.symmetricDifference(setB)
print(setC)
// print: ["B", "E", "F", "A"]

.subtracting() Subtraction

var setA: Set = ["A", "B", "C", "D"]
var setB: Set = ["C", "D"]

var setC = setA.subtracting(setB)
print(setC)
// print: ["B", "A"]

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