Swift for Rails Developers - Notes

Overview

My quick and dirty notes while watching Swift for Rails Developers

Ruby -vs Swift

• Runtimes

• Dynamic -vs- Static

• Mutability

• Optional Values / Null Handling

• Duck Typing

• Monkey Patching

Runtimes

• Ruby - IRB console

• Swift - Swift Playground

  • Xcode
  • File - New Playground

Dynamic -vs- Static

• Ruby - Dynamic

• Swift - Static

  • Can't change the type of something
  • x = 1
  • x = 'String' -> throws error
  • var name: String = 'Joe'
  • var double: Double = 1

Mutability

• Swift - let - prefer let over var

  • let name: String = 'Joe'
  • Prefer let (immutable) over var (mutable)

• Ruby - CONSTANT

Optional Values / Null Handling

 let dictionary: [
    "breakfast": "eggs",
    "lunch": "sandwich"
 ]

 let breakfast = dictionary["breakfast"]
'2x ' + breakfast

• force unwrap

  • let snack = dictionary["snack"]!
  • dangerous, snack doesn't exist, throws error

• null coalescing operator

  • let snack = dictionary["snack"] ?? "chips"

• optional unwrapping with if let

  • if let breakfast = dictionary["breakfast"] { '2x ' + breakfast }

Duck Typing

    # Ruby
    class Dog
        def say_hi
            'woof'
        end
    end
    class Cat
        def say_hi
            'meow'
        end
    end

    [Dog.new, Cat.new].each do |animal|
        puts animal.say_hi
    end

 class Dog {
    func sayHi() -> String {
        return "woof"
    }
 }
 class Cat {
    func sayHi() -> String {
        return "meow"
    }
 }


let animals = [Dog(), Cat()] // Heterogeneous collection

let animals: [Any] = [Dog(), Cat()] // Works but doesn't get us far

Instead we can use a protocol

protocol Animal {
    func sayHi() -> String
}

class Dog: Animal {
    func sayHi() -> String {
        return "woof"
    }
}
class Cat: Animal {
    func sayHi() -> String {
        return "meow"
    }
}
class Mouse: Animal {
    func sayHi() -> String {
        return "squeak"
    }
}

let animals: [Animal] = [Dog(), Cat(), Mouse()]

animals.forEach { animal in
    print(animal.sayHi())
}

Extensions (swift) -vs- Monkey Patching (ruby)

Powerfull way to add functionality to existing types from vendors etc.

protocol Animal {
    func sayHi() -> String
}

class Dog {
}

extension Dog: Animal {
    func sayHi() -> String {
        return "woof"
    }
}

Xcode Intro

Starting New Project

When building a Turbo Native Application, to start a Swift Project

• xCode

• File - New - Project

• iOS App - Next - Change Swift to Story Board

• Remove Boilerplate

  • App Delegate
  • Scene Delegate

Navigate Xcode

Project Navigator

• CMD 0 - Open / Close

• CMD 1 - File Explorer

• CMD 1-9 - Change Mode

• Single Click file open

• Double CLick file open and leave open

• CMD SHIFT 0 - Quick Open!

Properties / Inspector

• OPTION CMD 0 - Open / Close

• Usually leave close

Project File Structure

• AppDelegate.swift - throwback to objective C

  • func main - entry point to application
  • Don't need anything (Yet)
  • Future home of push notification registration

• SceneDelegate.swift

  • Gets called every time a new window gets opened.
  • func scene
  • Don't need to modify it really
  • window.backgroundColor = .systemGreen

• Running

  • Click Play in Navigator Bar
  • Runs new Instance of a simulator

Rails MVC - ios MVC

• in func scene

// SceneDelegate.swift
// func scene

let viewController = UIViewController()
window.rootViewController = viewController

• Subclass UIViewController

 class MyViewController: UIViewController {
    override func viewDidLoad() {
        super.viewDidLoad()
        let label = UILabel()
        label.text = "Hello World"
        label.sizeToFit()
        label.center = view.center
        view.addSubview(label)

    }
 }

Back in scene

 // SceneDelegate.swift
// func scene

let viewController = MyViewController()
window.rootViewController = viewController

Let's try to get more interactive

• Make Button

• Prints Logs when Clicked
  

 class MyViewController: UIViewController {
    override func viewDidLoad() {
        super.viewDidLoad()
        let button = UIButton(type: .system)
        button.setTitle("Tap Me", for: .normal)
        button.sizeToFit()
        view.addSubView(button)
        button.center = view.center

        button.addTarget(self, action: #selector(buttonWasTapped), for: .touchUpInside)
    }

    @objc private func buttonWasTapped() {
        print("Button was tapped")
    }
 }

Navigation Controller

• Understanding the Navigation Stack

• UIViewController on top NavigationController

• BaseNavigation

  • Index to Show
  • Show to Some Other Show Page

• To Wire Up

  • Get an Instance of Navigation Controller
  • Push UI Controllers

// SceneDelegate.swift
// func scene

let viewController = UIViewController()
let navigationController = UINavigationController(rootViewController: viewController)
window.rootViewController = viewController

 class MyViewController: UIViewController {
    override func viewDidLoad() {
        super.viewDidLoad()
        self.title "My View Controller"
        // ...
    }
 }

Create a 2nd View Controller

class SecondViewController: UIViewController {
    override func viewDidLoad() {
        super.viewDidLoad()
        self.title "Second View Controller"

        let labvel = UILabel()
        label.text = "Second View Controller"
        label.sizeToFit()

        view.addSubview(label)
        label.center = view.center
    }
 }

How do we get this on the stack

     @objc private func buttonWasTapped() {
        navigationController?.pushViewController(SecondViewController(), animated: true)
    }

All views by default are transparent, so we can make animations look better.

  class MyViewController: UIViewController {
    override func viewDidLoad() {
        super.viewDidLoad()
        view.backgroundColor = .white
        // ...
    }

  class SecondViewController: UIViewController {
    override func viewDidLoad() {
        super.viewDidLoad()
        view.backgroundColor = .white
        // ...
    }

Modals

• Modals slide up from the bottom, and are not part of the navigation stack

     @objc private func buttonWasTapped() {
        present(SecondViewController(), animated: true)
    }

• Modals can also have navigation

     @objc private func buttonWasTapped() {
        let navigationController = UINavigationController(rootViewController: SecondViewController())
        present(navigationController, animated: true)
    }