Damir Stuhec damirstuhec

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,

Following the tradition from last year, here's my complete list of all interesting features and updates I could find in Apple's OSes, SDKs and developer tools that were announced at this year's WWDC. This is based on the keynotes, the "What's New In ..." presentations and some others, Apple's release notes, and blog posts and tweets that I came across in the last few weeks.

If for some reason you haven't watched the talks yet, I really recommend watching at least the "State of the Union" and the "What's New In" intros for the platforms you're interested in. The unofficial WWDC Mac app is great way to download the videos and keep track of what you've already watched.

If you're interested, here are my WWDC 2015 notes (might be useful if you're planning to drop support for iOS 8 now and start using some iOS 9 APIs).

OSX → macOS 10.12 Sierra

Setting up iOS Universal Links

	disabled_rules: # rule identifiers to exclude from running
	- variable_name
	- nesting
	- function_parameter_count
	opt_in_rules: # some rules are only opt-in
	- control_statement
	- empty_count
	- trailing_newline
	- colon
	- comma

	enum HTTPStatusCodes: Int {
	// 100 Informational
	case Continue = 100
	case SwitchingProtocols
	case Processing
	// 200 Success
	case OK = 200
	case Created
	case Accepted
	case NonAuthoritativeInformation

	//
	// AppStoryboards.swift
	// AppStoryboards
	//
	// Created by Gurdeep on 15/12/16.
	// Copyright © 2016 Gurdeep. All rights reserved.
	//

	import Foundation
	import UIKit

	import UIKit

	class WorkoutButton: UIButton {

	override func imageRectForContentRect(contentRect: CGRect) -> CGRect {
	var imageFrame = super.imageRectForContentRect(contentRect)
	imageFrame.origin.x = CGRectGetMaxX(contentRect) - CGRectGetWidth(imageFrame)
	return imageFrame
	}

	import UIKit

	func singlePixelLine(at y: CGFloat, in rect: CGRect, topBias: Bool = true) {
	let offset = pixelUnit/2.0
	let adjustedY = round(from: y - offset, fraction: pixelUnit, down: topBias) + offset
	let line = makeLine(at: adjustedY, in: rect)
	strokePath(line, width: pixelUnit)
	}

	import Foundation

	// Extend String to support regex searching by conforming
	// to CustomStringConvertible
	extension String: CustomStringConvertible {
	public var description: String {return self}
	}

	// Regex support for keys
	public extension Dictionary where Key: CustomStringConvertible {

	import UIKit

	class FloatingButtonController: UIViewController {

	private(set) var button: UIButton!

	required init?(coder aDecoder: NSCoder) {
	fatalError()
	}

Damir Stuhec damirstuhec

A composable pattern for pure state machines with effects

OSX → macOS 10.12 Sierra

Setting up iOS Universal Links

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