Swift

Introduction

Here is my first dip into Apple and swift Swift Cheat Sheet
And the documentation Docs

Data Types

Here we have the following Primatives

• Int
• Float
• Double
• String
• Bool

Control

If Statements

No surprises

if a < 4 {
  print("we are here 1")
}
else if a == 4 && a < 3 {
  print("we are here 2")
}
else {
  print("we are here 3")
}

Switch Statements

var aCharacter = "a"
switch aCharacter {
   case "a":
      print("we are here a")
   case "b":
      print("we are here b")
   default:
      print("we are here not a or b")
}

Loops

Example for loop

var sum = 0
for index in 1..5 {
   sum += index 
   print(sum)
}

Example for while loop

var counter = 5
while counter  > 0 {
   print("hello")
   counter -= 1  
}

Example for repeat while loop

var counter = 5
repeat {
   print("hello")
   counter -= 1  
} while counter  > 0

Functions

Simple example

func foo() {
  print("Fred")
}
foo()

The argument label, the first argument, is just a name to use in place or variable name

func addTwoNumbers(
  arg1 para1:Int,
  arg2 para2:Int) -> Int {
  return para1 + para2
}
let sum = addTwoNumbers(arg: 2)
print(sum)

Collections

Arrays

Using Arrays

var d = ["dog", "cat", "bird"]

// Using standard for loop
for index in 0...(d.count -1) {
   print(d[index])
} 

// Alternatively
for item in d {
   print(item)
} 

// Declare empty
var e = [String]()

// Add or Remove
e.append(d)
e.remove(1)
e[0] = "turtle"

Dictionaries

Using a dictionary

// Initialize may values
var responseMessages = [200: "OK",
                        403: "Access forbidden",
                        404: "File not found",
                        500: "Internal server error"]

// Initialize empty
var emptyDict: [String: String] = [:]

// Another approach
var carDB = Dictionary[String:String]()
carDB["DTQ 9999"] = "iCar"
carDB["RPA 248"] = "Jag"

// Update
carDB["RPA 248"] = "Red Jag"

// Remove 
carDB["RPA 248"] = nil

// Iterate
for (license, car ) in carDB {
   print("\(car) has license \(license)")
}

Classes

Class vs Structs

Classes are always passed by reference and Structs are passed by value i.e.

let fred1 = MySalary(100)
let fred2 = fred1
fred1.setSalary(50)
print("Salary \(fred2)")
// Prints 50

Base Claas

class BlogPost {
  var title = ""
  var body = ""
  var counter = 0
  func addCounter() {
    counter += 1 
  }
}

let myPost = BlogPost()
myPost.title = "Hello"
myPost.body = "My Body"
myPost.addCounter()
print(myPost.counter)

Optional Properties

We can make properties optional. Like most languages we need to test

class BlogPost {
  var title:String?
  var body = "hey"
  var counter = 0
}
let post = BlogPost()

// We test like this.
if let actualTitle = post.title {
   print(actualTitle)
}

// If you know you have a value you can override
post.title = "we have a value"
actualTitle = post.title 
print(actualTitle!)

// Or 
if actualTitle == nil {
  print(actualTitle!)
}

Computed Properties

class BlogPost {
   
  var title:String?
  var author:String = "hey"

  // Computed Property
  if title != nil  &&  author != nil {
    return title! + " by " + author
  }
  else {
    return "Something was nil"
  }
}

Initialise (Constructor)

We use self in place of this for other languages. Don't forget about argument labels. Note more than one init() permitted

class Person {
  var name = ""
  var age = 0

  func init(_ name: String) {
    self.name = name
    self.age = 22
  }

  func init(_ name: String, _ age: Init) {
    self.name = name
    self.age = age
  }
}
var a Person("Bill", 21)

Convenience Initializewr

This allows you to create an initializer where maybe only one parameter is different. It must call a standard (designated) initializer

struct Scene {
  var minutes = 0
}

class Movie {
  var title: String
  var author: String
  var date: Int
  var scenes: [Scene]

  init(title: String, author: String, date: Int) {
    self.title = title
    self.author = author
    self.date = date
    scenes = [Scene]()
  }

  convenience init(title:String) {
    self.init(title:title, author: "Unknown", date:2016)
  }

  func addPage(page: Scene) {
    scenes.append(page)
  }
}


var myMovie = Movie(title: "my title") // Using convenicence initializer
var otherMovie = Movie(title: "My Title", author: "My Author", date: 12) // Using a long normal initializer

Inheritance

We do this using a colon

class ImprovedBlog : BlogPost {
  var title = ""
  var body = ""
  var numberOfLikes = 0
  func addNumberOfLikes() {
    numberOfLikes += 1 
  }
}

Override can be used and you can call the base implementation

class NewCar : Car {
  override func drive() {
    print("Printing my stuff")
    // Print base stuff 
    super.drive()
  }
}