My Notes – Introduction to Swift
Once in a while I find it useful to stretch myself in a new direction. Usually this is to scratch an itch for a pet project that I am interested in. I also think this can help break the rut we can all to easily fall into. To that end, I spent my 3 day weekend learning the Swift programming language. I used a Pluralsight course called Swift Fundamentals.
Full Disclosure
Pluralsight did not sponsor this post. I do get access to Pluralsight through their participation in the VMware vExpert program. I have been selected to be a vExpert for many years and they have been a constant supporter of that program and many others. I have found their content very helpful as I keep my skills up-to-date. They have a very wide variety of training topics. I found their Swift Fundamentals course extremely engaging. If you want to grow your skills – I highly recommend that you check them out.
What this page is – and isn’t
This page is a collection of notes that I took while going through the course. My intention is to review what I have learned about Swift when I have the time to write a real app.
This page is not a tutorial or guide. While I hope it contains enough illustrative snippets to be a reference, it will probably not serve as a tool to teach someone who has never programmed before.
Getting Started
Xcode is the best tool to use when learning Swift. It is free to download and use. It has a very useful feature called the Xcode Playground. This is an area where you can type and execute code i
n iterative steps to try out complex logic or new programming techniques before using them in a larger program. I found this tremendously useful as I went through the course. I am a hands-on learner and I frequently paused the training so I could type out the code in my Playground to make sure I had the syntax down. You can actually take the notes below and paste them into an Xcode playground on your own computer.
My Notes – Introduction to Swift
This code is also available on GitHub.
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//optional value - has value of Nil (keyword) - Nil is not equal to NullmiddleName = "Ryan"middleName = nil // can assign optional variable the value of Nilvar lastName = "Doe"//check fo Nilif middleName == nil { }if middleName != nil { //forced unwrap - must check for value first -doing this with a Nil value will cause runtime error var foo = middleName! print(foo)}//more concise method of checking - optional bindingif let myMiddleName = middleName { print (myMiddleName)} else { // theres no value}age = age + maxAge//data type conversion- must explicitly write code to do it-no automatic conversion of data types - for safer codevar score=1var highScore=100.0var newHighScore = Double(score)// Arrays// - Array - numerical index (0 based)// - Dictionary - key-value pair// - Set - unordered collection// there are more complex datastructures - these 3 are built into the languagevar myNames = ["John", "Jane", "Mary"]var myAges = [1,2,3,4]print (myNames[1])myNames[2] = "Iron Man"myNames.countmyNames.append("Flash")myNames.remove(at: 3) //also removeall,removefirst, removelastvar myCars: [String] = [] //array of strings - initialized as emptymyCars.append("Mustang")print(age - 5)print ("foo")print ("foo",terminator: "")print ("foo",terminator: "-")// operators// standard operations work as expected + - * = /// icrement/decrement not supported -- ++// Special operators ?? ... ..< -> ! ? ===// program controlvar myscore = 100if myscore > 10 { //true} else { //false}/* conditon must be true or false - zero or not zero does not work in swift a==b a!=b a>b < <= >= logical AND a==b && c!=d logical OR a> b || a>c can use parens for complex situations*/// switch statementsvar shoeSize: IntshoeSize = 8switch shoeSize {case 1,2,3: //list print("between 1 and 3")case 15...20: //range print("case between 15 and 20")case 5: print("five")case 4: print ("four")case _ where shoeSize > 6: //found on Internet print ("more than 6")default: print("something else")}//range operators// 1...10 - 1-10 closed range// 1..<10 - 1-9 half open - zero based arrays// range always goes up// single step increments// stride - function to increment in jumps - ie 16 at a time - 3 parameters - can move in reverse/* from - start through - end by - increment *///loops - 3 ways/* while repeat/while (replaces do-while) for/in */var items=3while items < 10 { print("something") items += 1}repeat { print ("something") items += 1} while items < 10let myColors = ["red","blue","green"]for thisColor in myColors { print (thisColor)}//string interpolation (ie: hacking up strings)var trackName = "Hail to the King"var artistName = "Avenge Sevenfold"var duration = 228let message = "Now Playing \(trackName) by \(artistName) which is \(duration / 60)m \(duration % 60)s long"//functions & methodsfunc showMessage(firstName: String, lastName: String) -> String { //parens are for params and required - even if no params //params are immutable (constant) print("hello \(firstName) \(lastName)") return "all done"}var myResult = showMessage(firstName: "Bob", lastName: "King")// function with "-> Void" returns nothing (optional should revist module 4 section3 to learn more)//call function but don't care about return value_ = showMessage(firstName: "Jane", lastName: "Doe")//un-named input params - underscore with space - cannot use param name when calling//not common or in swift mindset (clarity)func showMessage2(_ firstName: String, lastName: String) -> String { //parens are for params and required - even if no params //params are immutable (constant) print("hello \(firstName) \(lastName)") return "all done"}//different param name on function call vs inside function (from to:type)func showMessage3(firstName givenName : String, lastName surName: String) -> String { //parens are for params and required - even if no params //params are immutable (constant) print("hello \(givenName) \(surName)") return "all done"}var myResult3 = showMessage3(firstName: "John", lastName: "Doe")// Deeper Dive on data types//enumerations - data types begin with Upper Case letterenum MediaType { case book case movie case music case game // or case book, movie, music, game}var itemType: MediaTypeitemType = MediaType.game//shorthandvar newItemType: MediaTypenewItemType = .bookswitch newItemType {case .movie: print ("movie")case .game: print ("game")default: print ("book, or music")}// raw value// define as a string, can access as .rawValue// associated values// different data types defined in enum declarationenum newMediaType { case movie(String) case music(Int) case book(String)}var firstItem: newMediaType = .movie("Comedy")var secondItem: newMediaType = .music(120)switch firstItem {case .movie(let genre): print("It's a \(genre) movie")case .music (let bpm): print("The music is \(bpm) beats per minute")case .book (let author): print("It's by \(author)")}// Structures (struct)struct Movie { // properties var title: String var director: String var releaseYear: Int var genre: String //methods func summary() -> String { return "The movie \(title) was directed by \(director). It is an \(genre) movie and was released in \(releaseYear)." }}var favMovie = Movie(title: "Diamonds Are Forever", director: "Guy Hamilton", releaseYear: 1970, genre: "Action")print (favMovie.title)favMovie.releaseYear = 1971 //actual release year ;-)print(favMovie.summary())//Dictionaries - group of key-value pairs - in other languages could be Map, Symbol Table, Associative Array, or Dictionary// keys and values have distinct (and potentially differnt types)var airlines = ["SWA": "Southwest Airlines", "BAW": "British Airways", "DEL": "Delta Airlines"]var employees = [101: "John Doe", 20313: "Jane Doe", 23234: "Tony Stark"]if let result = airlines["SWA"] { //returns optional value as no guarantee of match print(result)} else { print("No Match Found")}//add or change - if no match found - addairlines["DVA"] = "Discovery Airlines"airlines["DVA"] = nil //removes key value pairfor (code, airline) in airlines { //syntax is called a tuple print("\(code) - \(airline)")}print("done")// tuple means several elements gathered together - quintuple, sextuple, etclet cameraType = "Canon"let photoMode = truelet shutterSpeed = 60let iso = 640let aperture = "f1.4"var basicTuple = (aperture, iso, cameraType)print(basicTuple)//useful to return multiple values from a functionfunc tupleExample() -> (name: String, age: Int) { return ("test string", 4)}let tupleResult = tupleExample()print(tupleResult)print(tupleResult.0)print(tupleResult.name)let (returnValueOne, returnValueTwo) = tupleResultprint(returnValueTwo)//Closures// take lines of code and group it together to use somewhere else in our program// block of code in {} has no name// do not call it - you pass it// a function is a closure with a name//// a bit challenging - very concise way of writing codestruct Book { var title: String var authorLastName: String var authorFirstName: String var readingAge: Int var pageCount: Int}let book1 = Book.init(title: "The Hobbit", authorLastName: "Tokien", authorFirstName: "J.R.R", readingAge: 12, pageCount: 300)let book2 = Book.init(title: "Centaur Isle", authorLastName: "Anthony", authorFirstName: "Piers", readingAge: 9, pageCount: 320)let book3 = Book.init(title: "Enchanter's End Game", authorLastName: "Eddings", authorFirstName: "David", readingAge: 14, pageCount: 275)let book4 = Book.init(title: "Ender's Game", authorLastName: "Card", authorFirstName: "Orson Scott", readingAge: 19, pageCount: 300)let allBooks = [book1, book2, book3, book4]// some functions requires closures//going to sort - using SortedBy/* - very verbose closure - helpful to learn basics but not used in practice func compareTwoBooks (firstBook: Book, secondBook: Book) -> Bool { if firstBook.readingAge <= secondBook.readingAge { return true } else { return false }}let ageSortedBooks = allBooks.sorted(by: compareTwoBooks)ageSortedBooks *///more normal closure - closure code in braces - inside of .sorted call// still very verbose - gets much more simplified in practice/*let ageSortedBooks = allBooks.sorted(by: { (firstBook: Book, secondBook: Book) -> Bool in if firstBook.readingAge <= secondBook.readingAge { return true } else { return false }})ageSortedBooks */// trailing closure - used when closure is only or last argument -//removes much redundant syntax - returnlet ageSortedBooks = allBooks.sorted { $0.readingAge <= $1.readingAge }ageSortedBookslet booksForUnder14s = allBooks.filter { $0.readingAge < 14}booksForUnder14s// Classes and Objectsclass Appliance { //properties // can initialize at declaration - var manufacturer: String = "" var manufacturer: String var model: String var voltage: Int var capacity: Int? //initializer init() { //specializer method - called automatically when instantiated //takes no parameters self.manufacturer = "default manufacturer" self.model = "default model" self.voltage = 120 } //can have addtional initializers as long as they have different parameter signatures //deinitializer deinit { // not needed most of the time. can be used to do clean up. only allowed in a class - not in a struct //swift uses Arc - Automatic Reference Coutning to automatically cleanup and deallocating memory - deinit called at this time } //methods func getDetails() -> String { var message = "This is the \(self.model) from \(self.manufacturer)." if self.voltage >= 220 { message += "This model is for European usage." } return message } }var kettle = Appliance()kettle.manufacturer = "Samsung"//kettle.model = "TeaMaster 5000"kettle.voltage = 120print(kettle.getDetails())/* difference between structs and classes with structs, if value is assigned to a new variable (or constant) or passed into a function - the value is copied will classes, those values are not copied - they are passed as a reference the === (identity operator) can help verify if two different instances(variables) are pointing to the same thing */ class Toaster: Appliance { //note case of class name and : (: indicates inheritance) //this is a subclass of superclass Appliance // new properties var slices: Int override init() { //inherited classes could already have an init method and must user override - original init still called (first) thne this init self.slices = 2 // super. can be used to over ride the original init // keyword final can be used in super class to prevent changes by subclasses } //new method func toast() { print("Irradiating now...") } }var myToaster = Toaster()myToaster.manufacturer = "AcmeCorp"myToaster.model = "Carbonizer"myToaster.getDetails()myToaster.toast()// Extensions//stringsextension String { func removeSpaces() -> String { let filteredCharacters = self.filter {$0 != " "} return String(filteredCharacters) }}let album = "Decks and drums and rock and roll"let phrase = "Love is now here"print(album.removeSpaces())print(phrase.removeSpaces())// Stored Properties - Computed Propertiesclass Player { // stored properties var name: String var livesRemaining: Int var enemiesDestroyed: Int var penalty: Int var bonus: Int //computed property var score: Int { get { return (enemiesDestroyed * 1000) + bonus + (livesRemaining * 5000) - penalty } //can also have set {} to set this property - not useful in this specific case // if no get{} or set {} - swift assumes get - very concise } //initialize init(name: String) { self.name = name self.livesRemaining = 3 self.enemiesDestroyed = 0 self.penalty = 0 self.bonus = 0 }}let newPlayer = Player(name: "Ava")newPlayer.enemiesDestroyed = 327newPlayer.penalty = 872newPlayer.bonus = 48000print("The final score for \(newPlayer.name) is \(newPlayer.score)")// Protocols/* swift is a protocol-oriented programming lanuage inheritance can be done; but not common - more common to write extensions protocol here is more about Standard operating procedure in the language or frameworks vs https/tcp/etcprotocols are adopted - this is done on class declaration line. can adopt multiple protocols */class Player2: CustomStringConvertible { //adopting the protocol // stored properties var name: String var livesRemaining: Int var enemiesDestroyed: Int var penalty: Int var bonus: Int //required byt his specific protocol - this "conforms" to the protocol var description: String { return "Player \(self.name) has a score of \(self.score) and \(self.livesRemaining) lives remaining." } //computed property var score: Int { get { return (enemiesDestroyed * 1000) + bonus + (livesRemaining * 5000) - penalty } //can also have set {} to set this property - not useful in this specific case // if no get{} or set {} - swift assumes get - very concise } //initialize init(name: String) { self.name = name self.livesRemaining = 3 self.enemiesDestroyed = 0 self.penalty = 0 self.bonus = 0 }}let mynewPlayer = Player2(name: "Joey")mynewPlayer.enemiesDestroyed = 327mynewPlayer.penalty = 872mynewPlayer.bonus = 48000print("The final score for \(mynewPlayer.name) is \(mynewPlayer.score)")//print the instance of Player2 - to invoke the desscription property - required by the CustomStringConvertible protocolprint(mynewPlayer)//Define a protocolprotocol MyProtocol { //what methods are required func showMessages() //what properties var name: String {get set} //get-read set-write}//handling errors in swift - adopting that protocol//dealing with recoverable errors/* define error - waht is it throw it - where and when will it happen handle it - recover swift does not provide a built-in error class */enum ServerError: Error { // define the error case noConnection case serverNotFound case authenticationRefused //no parameters or methods to conform }func checkStatus(serverNumber: Int) throws -> String { // note the keyword throws switch serverNumber { case 1: print("You have no connoection.") throw ServerError.noConnection case 2: print("Authentication failed.") throw ServerError.authenticationRefused case 3: print("Server is up and running.") default: print("Can't find that server.") throw ServerError.serverNotFound } return "Success!"}// normal function call - but since it can throw an error must handle differently//let result = checkStatus(serverNumber: 1)//print(result)do { let result = try checkStatus(serverNumber: 4) print(result)} catch ServerError.noConnection { //no connection print("No Connection")} catch ServerError.authenticationRefused { //authentication error print("Your password is wrong.")} catch { print("The problem is : \(error)")}// if error isn't super important you can make it optionallet result2: String?/* long form do { result2 = try checkStatus(serverNumber: 3)} catch { result2=nil} if result2 != nil { print(result2!)} */if let result3 = try? checkStatus(serverNumber: 1) { print(result3) //will return nil if no error}// Guard and Defer - control flow statements//Guard - close in spirit to if/elsefunc processTrack(trackName: String?, artist: String?, duration: Int?) { //need to check if the params are nil. can do with multiple nested if statements (pyramid of doom) but clunky guard true else { //what we do if this isn't true //need to have hard exit - return /throw / break } /* guard let unwrappedname = trackName else { return } - exits if trackName == nil */ // Defer /* func processCart (myCart: ShoppingCart) { //open the resource myCart.open() defer { //this block of code will always be called before this funciton exits myCart.close() } other lines of code } */} |