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

2. 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

3. 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

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

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

6. 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

7. 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

8. 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

9. 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!).") }

10. 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

11. 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"

12. 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)")

13. 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 */ }

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

15. 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)")

16. 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

17. 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"]

18. 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

19. References Swift 3 Programming Language Guide
Swift Blog
Online Swift REPL