Mutability of Collections: Arrays
Swift
// creata an empty arrayvar someInts = [Int]()print("someInts is of type [Int] with \(someInts.count) items.")// Prints "someInts is of type [Int] with 0 items."
// Creating an Array with a Default Valuevar threeDoubles = Array(repeating: 0.0, count: 3)// threeDoubles is of type [Double], and equals [0.0, 0.0, 0.0]var anotherThreeDoubles = Array(repeating: 2.5, count: 3)// anotherThreeDoubles is of type [Double], and equals [2.5, 2.5, 2.5]
var sixDoubles = threeDoubles + anotherThreeDoubles// sixDoubles is inferred as [Double], and equals [0.0, 0.0, 0.0, 2.5, 2.5, 2.5]
// Creating an Array with an Array Literalvar shoppingList: [String] = ["Eggs", "Milk"]// shoppingList has been initialized with two initial items
// Accessing and Modifying an Arrayif shoppingList.isEmpty {print("The shopping list is empty.")} else {print("The shopping list is not empty.")}// Prints "The shopping list is not empty."shoppingList.append("Flour")// shoppingList now contains 3 items, and someone is making pancakesshoppingList += ["Baking Powder"]// shoppingList now contains 4 itemsshoppingList += ["Chocolate Spread", "Cheese", "Butter"]// shoppingList now contains 7 itemsvar firstItem = shoppingList[0]
// firstItem is equal to "Eggs"shoppingList[0] = "Six eggs"// the first item in the list is now equal to "Six eggs" rather than "Eggs"
shoppingList[4...6] = ["Bananas", "Apples"]// shoppingList now contains 6 items
shoppingList.insert("Maple Syrup", at: 0)// shoppingList now contains 7 items// "Maple Syrup" is now the first item in the list
let mapleSyrup = shoppingList.remove(at: 0)// the item that was at index 0 has just been removed// shoppingList now contains 6 items, and no Maple Syrup// the mapleSyrup constant is now equal to the removed "Maple Syrup" string
let apples = shoppingList.removeLast()// the last item in the array has just been removed// shoppingList now contains 5 items, and no apples// the apples constant is now equal to the removed "Apples" string
// Iterating Over an Arrayfor item in shoppingList {print(item)}// Six eggs// Milk// Flour// Baking Powder// Bananas
for (index, value) in shoppingList.enumerated() {print("Item \(index + 1): \(value)")}// Item 1: Six eggs// Item 2: Milk// Item 3: Flour// Item 4: Baking Powder// Item 5: Bananas
JavaScript
// creata an empty arraylet someInts = new Array()console.log(`someInts is an array with ${someInts.length} items.`)// Prints "someInts is an array with 0 items."
// Creating an Array with a Default Valuelet threeDoubles = [0.0, 0.0, 0.0]// threeDoubles is of type [Double], and equals [0.0, 0.0, 0.0]let anotherThreeDoubles = [2.5, 2.5, 2.5]// anotherThreeDoubles is of type [Double], and equals [2.5, 2.5, 2.5]
let sixDoubles = [...threeDoubles, ...anotherThreeDoubles]// sixDoubles is inferred as [Double], and equals [0.0, 0.0, 0.0, 2.5, 2.5, 2.5]
// Creating an Array with an Array Literallet shoppingList = ["Eggs", "Milk"]// shoppingList has been initialized with two initial items
// Accessing and Modifying an Arrayif (shoppingList.length === 0) {console.log("The shopping list is empty.")} else {console.log("The shopping list is not empty.")}// Prints "The shopping list is not empty."shoppingList.push("Flour")// shoppingList now contains 3 items, and someone is making pancakesshoppingList = shoppingList.concat(["Baking Powder"])// shoppingList now contains 4 itemsshoppingList = [...shoppingList, "Chocolate Spread", "Cheese", "Butter"]// shoppingList now contains 7 itemslet firstItem = shoppingList[0]// firstItem is equal to "Eggs"shoppingList[0] = "Six eggs"// the first item in the list is now equal to "Six eggs" rather than "Eggs"
shoppingList.splice(4, 3, "Bananas", "Apples")// shoppingList now contains 6 items
shoppingList.unshift("Maple Syrup")// shoppingList now contains 7 items// "Maple Syrup" is now the first item in the list
let mapleSyrup = shoppingList.shift()// the item that was at index 0 has just been removed// shoppingList now contains 6 items, and no Maple Syrup// the mapleSyrup constant is now equal to the removed "Maple Syrup" string
let apples = shoppingList.pop()// the last item in the array has just been removed// shoppingList now contains 5 items, and no apples// the apples constant is now equal to the removed "Apples" string
// Iterating Over an ArrayshoppingList.forEach((item => {console.log(item)})// Six eggs// Milk// Flour// Baking Powder// Bananas
shoppingList.forEach(((item, index) => {console.log(`Item ${index + 1}: ${value}`)})// Item 1: Six eggs// Item 2: Milk// Item 3: Flour// Item 4: Baking Powder// Item 5: Bananas
Sets
Swift
// Creating and Initializing an Empty Setvar letters = Set<Character>()print("letters is of type Set<Character> with \(letters.count) items.")// Prints "letters is of type Set<Character> with 0 items."var favoriteGenres: Set<String> = ["Rock", "Classical", "Hip hop"]// favoriteGenres has been initialized with three initial items
// Accessing and Modifying a Setprint("I have \(favoriteGenres.count) favorite music genres.")// Prints "I have 3 favorite music genres."
if favoriteGenres.isEmpty {print("As far as music goes, I'm not picky.")} else {print("I have particular music preferences.")}// Prints "I have particular music preferences."
favoriteGenres.insert("Jazz")// favoriteGenres now contains 4 items
if let removedGenre = favoriteGenres.remove("Rock") {print("\(removedGenre)? I'm over it.")} else {print("I never much cared for that.")}// Prints "Rock? I'm over it."
if favoriteGenres.contains("Funk") {print("I get up on the good foot.")} else {print("It's too funky in here.")}// Prints "It's too funky in here."
// Iterating Over a Setfor genre in favoriteGenres {print("\(genre)")}// Classical// Jazz// Hip hop
JavaScript
// Creating and Initializing an Empty Setlet letters = new Set()console.log(`letters is of type Set with ${letters.size} items.`)// Prints "letters is of type Set with 0 items."let favoriteGenres = new set(["Rock", "Classical", "Hip hop"])// favoriteGenres has been initialized with three initial items
// Accessing and Modifying a Setconsole.log(`I have ${favoriteGenres.size} favorite music genres.`)// Prints "I have 3 favorite music genres."
if (favoriteGenres.size == 0) {console.log("As far as music goes, I'm not picky.")} else {console.log("I have particular music preferences.")}// Prints "I have particular music preferences."
favoriteGenres.add("Jazz")// favoriteGenres now contains 4 itemsconst removedGenre = favoriteGenres.delete("Rock")if (removedGenre) {console.log(`${removedGenre}? I'm over it.`)} else {console.log("I never much cared for that.")}// Prints "Rock? I'm over it."
if (favoriteGenres.has("Funk")) {console.log("I get up on the good foot.")} else {console.log("It's too funky in here.")}// Prints "It's too funky in here."
// Iterating Over a SetfavoriteGenres.forEach(genre => {console.log(genre);})// Classical// Jazz// Hip hop
Dictionaries
Swift
// Creating an Empty Dictionaryvar namesOfIntegers = [Int: String]()// namesOfIntegers is an empty [Int: String] dictionarynamesOfIntegers[16] = "sixteen"// namesOfIntegers now contains 1 key-value pairnamesOfIntegers = [:]// namesOfIntegers is once again an empty dictionary of type [Int: String]
// Creating a Dictionary with a Dictionary Literalvar airports: [String: String] = ["YYZ": "Toronto Pearson", "DUB": "Dublin"]
// Accessing and Modifying a Dictionaryprint("The airports dictionary contains \(airports.count) items.")// Prints "The airports dictionary contains 2 items."
if airports.isEmpty {print("The airports dictionary is empty.")} else {print("The airports dictionary is not empty.")}// Prints "The airports dictionary is not empty."
airports["LHR"] = "London"// the airports dictionary now contains 3 items
airports["LHR"] = "London Heathrow"// the value for "LHR" has been changed to "London Heathrow"
if let oldValue = airports.updateValue("Dublin Airport", forKey: "DUB") {print("The old value for DUB was \(oldValue).")}// Prints "The old value for DUB was Dublin."
if let airportName = airports["DUB"] {print("The name of the airport is \(airportName).")} else {print("That airport is not in the airports dictionary.")}// Prints "The name of the airport is Dublin Airport."
airports["APL"] = "Apple International"// "Apple International" is not the real airport for APL, so delete itairports["APL"] = nil// APL has now been removed from the dictionary
if let removedValue = airports.removeValue(forKey: "DUB") {print("The removed airport's name is \(removedValue).")} else {print("The airports dictionary does not contain a value for DUB.")}// Prints "The removed airport's name is Dublin Airport."
// Iterating Over a Dictionaryfor (airportCode, airportName) in airports {print("\(airportCode): \(airportName)")}// YYZ: Toronto Pearson// LHR: London Heathrow
for airportCode in airports.keys {print("Airport code: \(airportCode)")}// Airport code: YYZ// Airport code: LHR
for airportName in airports.values {print("Airport name: \(airportName)")}// Airport name: Toronto Pearson// Airport name: London Heathrow
let airportCodes = [String](airports.keys)// airportCodes is ["YYZ", "LHR"]
let airportNames = [String](airports.values)// airportNames is ["Toronto Pearson", "London Heathrow"]
JavaScript
// Creating an Empty Dictionarylet namesOfIntegers = {}// namesOfIntegers is an empty dictionarynamesOfIntegers[16] = "sixteen"// namesOfIntegers now contains 1 key-value pairnamesOfIntegers = {}// namesOfIntegers is once again an empty dictionary of type
// Creating a Dictionary with a Dictionary Literallet airports = {"YYZ": "Toronto Pearson", "DUB": "Dublin"}
// Accessing and Modifying a Dictionaryconsole.log(`The airports dictionary contains ${Object.keys(airports).length} items.`)// Prints "The airports dictionary contains 2 items."
if (Object.keys(airports).length == 0) {console.log("The airports dictionary is empty.")} else {console.log("The airports dictionary is not empty.")}// Prints "The airports dictionary is not empty."
airports["LHR"] = "London"// the airports dictionary now contains 3 items
airports["LHR"] = "London Heathrow"// the value for "LHR" has been changed to "London Heathrow"
const oldValue = airports["DUB"]airports["DUB"] = "Dublin Airport"if (oldValue) {console.log(`The old value for DUB was ${oldValue}.`)}// Prints "The old value for DUB was Dublin."const airportName = airports["DUB"]if (airportName) {console.log(`The name of the airport is ${airportName}.`)} else {console.log("That airport is not in the airports dictionary.")}// Prints "The name of the airport is Dublin Airport."
airports["APL"] = "Apple International"// "Apple International" is not the real airport for APL, so delete itairports["APL"] = nulldelete airports["APL"]// APL has now been removed from the dictionary
// Iterating Over a DictionaryObject.keys(airports).forEach(airportCode => {const airportName = airports[airportCode]console.log(`${airportCode}: ${airportName}`)})// YYZ: Toronto Pearson// LHR: London Heathrow
let airportCodes = Object.keys(airports)// airportCodes is ["YYZ", "LHR"]