Lecture 1 - Intro to Swift Ioannis Pavlidis Dinesh Majeti Ashik Khatri

Swift - Evolution Development on Swift was begun in July 2010 by Chris Lattner, Version 1.0 released on September 9, 2014 Swift 2.0 announced at WWDC 2015; made available for publishing apps in September 21, 2015. Swift made open source on December 3, 2015 A Swift 3.0 is expected to be released in Fall 2016

Swift - Overview General-purpose, multi-paradigm, compiled programming language. Object-oriented language with functional concepts. Typing discipline: Static, Strong, Inferred. File names end with .swift

Constants and Variables let maximumNumberOfLoginAttempts = 10 var currentLoginAttempt = 0 let myDoubleArray = [2.1, 3.5, 1.1] Type Annotations var welcomeMessage: String

Operators Supports all standard Arithmetic, Comparison, Logical, Bitwise, Assignment, Range (0..<3) Operators Supports Ternary Conditional ( Condition ? X : Y ). Unary Plus and Minus

Strings String Interpolation let multiplier = 3 let message = "\(multiplier) times 2.5 is \(Double(multiplier) * 2.5)" // message is “3 times 2.5 is 7.5” Can be applied to print statements String Concatenation let str = "Hello" + " swift lovers" // "Hello swift lovers" Methods on string print(str.characters.count) // 18

Optionals? You use optionals in situations where a value may be absent. An optional says: There is a value, and it equals x OR There isn’t a value at all Example: var serverResponseCode: Int? = 404 Optional variable can be set to nil (absence of a value of a certain type. Not a pointer) Example: serverResponseCode = nil nil cannot be used with non-optional constants and variables Optional variable without providing a default value: var surveyAnswer: String? // surveyAnswer is automatically set to nil

Control Flows If-else statements Supports switch statements if x >= y { print(“x is greater or equal to y”) } else { print(“y is greater”) Supports switch statements

Control Flows - unwrapping optionals let possibleNumber = "123" // possibleNumber is type String let convertedNumber = Int(possibleNumber) // convertedNumber is type Int? if convertedNumber != nil { // now that we know that convertedNumber has a value, force unwrap using “!” print("convertedNumber has integer value of \(convertedNumber!).") }

Control Flows - Optional Binding - I Use to find out whether an optional contains a value, and if so, to make that value available as a temporary constant or variable. Can be used with if and while statements if let actualNumber = Int(possibleNumber) { print("\"\(possibleNumber)\" has an integer value of \(actualNumber)") } else { print("\"\(possibleNumber)\" could not be converted to an integer") } // Prints "123" has an integer value of 123

Control Flows - Optional Binding - II Can also include multiple optional bindings in a single if statement if let firstNumber = Int("4"), secondNumber = Int("42") where firstNumber < secondNumber { print("\(firstNumber) < \(secondNumber)") } // Prints "4 < 42"

Control Flows - Early Exit A guard statement, like an if statement, executes statements depending on the Boolean value of an expression. Unlike an if statement, a guard statement always has an else clause func foo(possibleNumber : String?) { guard let actualNumber = Int(possibleNumber) else { return } print("Number is: \(actualNumber)")

Control Flows - Loops Swift supports for, for-in, while, and do...while loops for var index = 0; index < 3; index += 1 { … } for item in someArray { … } while index < 20 { … } do { … } while index < 20 for i in 0..<3 { /* this will loop 3 times */ }

Functions - I func sayHello(personName: String) -> String { return "Hello, " + personName + "!" } print(sayHello("Bob")) // Prints "Hello, Bob! Supports nested functions → Create function inside a function!

Functions - II Functions with Multiple Return Values func minMax(array: [Int]) -> (min: Int, max: Int) { var currentMin = array[0] var currentMax = array[0] // some logic ... return (currentMin, currentMax) } let bounds = minMax([8, -6, 2, 109, 3, 71]) print("min is \(bounds.min) and max is \(bounds.max)")

Closures - I Closures are self-contained blocks of functionality that can be passed around and used in your code. { (<parameters>) -> <return type> in <statements> } Functions are actually special cases of closures. global functions – they have a name and cannot capture any values nested functions – they have a name and can capture values from their enclosing functions closure expressions – they don’t have a name and can capture values from their context

Closures - II Example: let names = ["Chris", "Alex", "Ewa", "Barry", "Daniella"] let sorted = names.sort() // ["Alex", "Barry", "Chris", "Daniella", "Ewa"] let reversed1 = names.sort({ (s1: String, s2: String) -> Bool in return s2 > s2 }) // ["Ewa", "Daniella", "Chris", "Barry", "Alex"] let reversed2 = names.sort({s1, s2 in s1 > s2}) // ["Ewa", "Daniella", "Chris", "Barry", "Alex"] let reversed3 = names.sort(>) // ["Ewa", "Daniella", "Chris", "Barry", "Alex"]

Classes class Person { var name: String var gender = “Male” var age: Int? init(name: String) { self.name = name } // other functions and variables … … let bob = Person(name: “Bob”) bob.age = 18

References Swift 3 Programming Language Guide Swift Blog Online Swift REPL