An introduction to programming. In Swift.

SwiftIntro.swift

// This is a comment. The computer will ignore everything after a double slash.

//  ---- Hello World ----
print("Hello world!")

var numPlanetsInSolarSystem = 8
var floatVariableName = 4.3

// Integers
var five = 2 + 3
var three = 7 / 2
var threeAndAHalf = 7.0 / 2.0

// Strings
var myName = "Your Name"
print("Hello! My name is " + myName) // This is how we "add" strings

// Booleans
var wittyBoolName = true

var moonDistance = 370300
var astronautDistance = 295322

var astronautArrivedToMoon = moonDistance <= astronautDistance
// astronautArrivedToMoon is false, becuase the moonDistance is greater than astronautDistance

// Printing
print(4+3)


// Variables
var numberOfPlanets = 9
numberOfPlanets = numberOfPlanets - 1 // numberOfPlanets is now 8
print("We now have \(numberOfPlanets) planets. We'll miss you Pluto.")
numberOfPlanets -= 1 // This is the short form of the line above
// numberOfPlanets is now 7. :o

// We can also double the number of apples:
var numberOfSpaceRockets = 3
print("We start off with \(numberOfSpaceRockets) rockets.")
numberOfSpaceRockets *= 2
print("Woah! We suddenly have \(numberOfSpaceRockets) rockets! Thanks Elon!")

// Constants
let zero = 0 // Will always be 0. Forever.

// If statements
var condition = true
if (condition) {
    print("The condition was true")
}

var firstNum = 3
var secondNum = 2
if (firstNum > secondNum) {
    print("firstNum is greater than secondNum")
} else {
    print("firstNum is less than or equal to secondNum")
}

var cond1 = false
var cond2 = true
if (cond1) {
    print("Cond1 is true")
} else if (cond2) {
    print("Cond1 is false, but cond2 is true")
} else {
    print("Cond1 and cond2 are both false")
}


// While loop
var countdown = 10
while (countdown > 0) {
    print(countdown)
    countdown -= 1
}
print("Blastoff!")


// Types
var name: String = "My Name"

// Lists
var list = [1,2,3,4]
var anotherlist = 1...4 // A shortcut in Swift that does the same as above
var crew = ["Joe", "Sarah", "Dave"] // Lists can hold anything, as long as they are the same type

crew = ["Joe", "Sarah", "Dave"]
var firstCosmonaut = crew[0] // joe
var secondCosmonaut = crew[1] // sarah

crew = ["Joe", "Sarah", "Dave"]
crew[0] = "Alice"
print(crew)

crew = ["Jason", "Sarah", "Dave"]
crew.append("Cora")
print(crew)

// Dictionaries
var dictionary = ["spaceship":"vehicle to get around space time", "astronaut":"space explorer"]
var spaceShipDefinition = dictionary["spaceship"]
print(spaceShipDefinition) // prints "vehicle to get around space time"

// As long as they are variables, they can be change just like lists
dictionary["astronaut"] = "space wanderer"

// More types
var engineeringTeam: [String] = ["First Member", "Second Member"] // this is an array of strings
var yearsAtNasa: [String:Int] = ["First Member":2, "Second Member":1] // this is a dictionary from strings to ints

var engineersInSpace = [String]()

// For loops
crew = ["Joe", "Sarah", "Dave"]
for crewMember in crew {
    print("\(crewMember) is in the crew")
}

// Optionals
var optional: [String]? = nil
// optional!.count // CRASH

optional = ["hi", "hello"]
optional?.count

// Functions
func methodWithFirstArgument(a: Int, andSecondArgument b: Int) {
    print("This is a common way to pass \(a) and \(b) into a function in Swift")
}

func introduce(name: String) {
    print("Hello my name is " + name)
}

func add(a: Int,_ b: Int) -> Int {
    return a + b
}


methodWithFirstArgument(42, andSecondArgument: 13)
introduce("Jonathan")
var seven = add(4, 3)


// Objects
class Person {
    var name: String
    var age: Int
    
    // The initializer is the function that creates the object
    // You need at least one initializer for every class
    init(givenName: String, givenAge: Int) {
        // We can access the properties of an object using dot notation as below
        // "self" is how we refer to the current instance of the class
        self.name = givenName
        self.age = givenAge
    }
    
    func introduce() {
        print("Hello! My name is \(self.name) and I am \(self.age) years old. Nice to meet you.")
    }
}

var person = Person(givenName: "Alex", givenAge: 16)
person.introduce() // Call a method like this
var personAge = person.age // Access properties like this
person.age += 1 // Change properties like this. Happy birthday!

// Inheritance
class Astronaut: Person {
    var yearsInSpace: Int = 0
    var authorizedVehicles = ["Space Shuttle", "Soyuz"]
    
    func canFly(vehicle: String) -> Bool {
        return authorizedVehicles.contains(vehicle)
    }
}

// Protocols
class Vehicle { // A generic Vehicle class
    let numberOfWheels: Int
    var speed = 0
    
    init(numberOfWheels: Int) {
        self.numberOfWheels = numberOfWheels
    }
}

protocol Flyable { // A Flyable protocol.
    var distanceOffGround: Int { get set }
    
    func land()
}

class SpaceShip: Vehicle, Flyable { // A SpaceShip is a Flyable vehicle
    var distanceOffGround: Int = 0
    
    func land() {
        self.speed = 0
        self.distanceOffGround = 0
    }
}