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)
    }

Blog

Swift for Rails Developers - Notes

Jeffrey Hicks