andymatuschak

A composable pattern for pure state machines with effects

State machines are everywhere in interactive systems, but they're rarely defined clearly and explicitly. Given some big blob of code including implicit state machines, which transitions are possible and under what conditions? What effects take place on what transitions?

There are existing design patterns for state machines, but all the patterns I've seen complect side effects with the structure of the state machine itself. Instances of these patterns are difficult to test without mocking, and they end up with more dependencies. Worse, the classic patterns compose poorly: hierarchical state machines are typically not straightforward extensions. The functional programming world has solutions, but they don't transpose neatly enough to be broadly usable in mainstream languages.

Here I present a composable pattern for pure state machiness with effects,

andyyhope

// Swift: Syntax Cheat Codes
// ↑ ↑ ↓ ↓ ← → ← → B A
//
// Author: Andyy Hope
// Twitter: @andyyhope
// Medium: medium.com/@andyyhope


import UIKit

steipete

# The trick is to link the DeviceSupport folder from the beta to the stable version.
# sudo needed if you run the Mac App Store version. Always download the dmg instead... you'll thank me later :)

# Support iOS 15 devices (Xcode 13.0) with Xcode 12.5:
sudo ln -s /Applications/Xcode-beta.app/Contents/Developer/Platforms/iPhoneOS.platform/DeviceSupport/15.0 /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/DeviceSupport

# Then restart Xcode and reconnect your devices. You will need to do that for every beta of future iOS versions

# (A similar approach works for older versions too, just change the version number after DeviceSupport)

JaviSoto

final class SampleViewController: StoryboardBackedViewController {
    // Unfortunately this must be an IUO var, so that we can set the value after super.init
    private var member: Foo!
    
    // Proper dependency injection in a storyboard backed VC!
    init(foo: Foo) {
        super.init(storyboardIdentifier: "SampleViewControllerIdentifier")

        // We have to set the members *after* calling super.init, since it changes the instance of `self`.
        self.member = foo

gwengrid

class Thunder { }
class Fire { }

protocol Pokemon {
    typealias PokemonType
    func attack(move:PokemonType)
}

struct Pikachu: Pokemon {
    typealias PokemonType = Thunder

aciidgh

import Foundation

public func getASTString() -> String {
    
    // get the file path for the file "test.json" in the playground bundle
    // let filePath = NSBundle.mainBundle().pathForResource("FirstTtest", ofType: "ast")
    
    // get the contentData
    let contentData = NSFileManager.defaultManager().contentsAtPath("a.txt")
    

chriseidhof

// gem install cocoapods-playgrounds
// pod playgrounds LibYAML

// Update: @floriankugler had a great idea to use UnsafeBufferPointer

// Paste in the following:

import LibYAML

public struct YAMLError: ErrorType {

tryvin

<script src="http://static.tumblr.com/fpifyru/VCxlv9xwi/writecapture.js"></script>
<script type="text/javascript">
    $(function() {
        $("a[href]").each(
            function(index, element) {
                if ( $(element).attr('href').indexOf('gist.github.com') > 0 ) {
                    var divElement = $('<div></div>');
                    $(element).after(divElement);

                    writeCapture.html(divElement, '<script src="'+$(element).attr('href')+'.js"></'+'script>');

natecook1000

// (c) 2015 Nate Cook, licensed under the MIT license
//
// Initializers for Dictionary like NSDictionary +dictionaryWithObjects:forKeys:

public extension Dictionary {
    /// Creates a new Dictionary from the given `keys` and `values` collections.
    ///
    /// More efficient than the sequence version because it can reserve the correct
    /// capacity before filling the dictionary. Returns `nil` if the lengths of the
    /// two collections differ.

eliperkins

//: Mocks Playground

import UIKit

struct User {
}

struct PushNotificationController {
    let registrar: PushNotificationRegistrar
    init(registrar: PushNotificationRegistrar) {