Stijn Willems doozMen

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,

	#!/bin/bash
	#
	# Build and iPhone Simulator Helper Script
	# Shazron Abdullah 2011
	#
	# WARN: - if your .xcodeproj name is not the same as your .app name,
	# this won't work without modifications
	# - you must run this script in where your .xcodeproj file is

	PROJECTNAME=$1

	@interface NSManagedObject (Serialization)

	- (NSDictionary*) toDictionary;

	- (void) populateFromDictionary:(NSDictionary*)dict;

	+ (NSManagedObject) createManagedObjectFromDictionary:(NSDictionary)dict
	inContext:(NSManagedObjectContext*)context;

	@end

	import Foundation

	/// An abstract class that makes building simple asynchronous operations easy.
	/// Subclasses must implement `execute()` to perform any work and call
	/// `finish()` when they are done. All `NSOperation` work will be handled
	/// automatically.
	open class AsynchronousOperation: Operation {

	// MARK: - Properties

	//
	// CoreDataFetchController.swift
	//
	// Created by Scott Grosch on 12/18/14.
	// Copyright (c) 2014 Gargoyle Software, LLC. All rights reserved.
	//

	import CoreData

	final class CoreDataFetchController<T : NSManagedObject> {

	//
	// Layout.swift
	//
	// Created by Stijn Willems on 10/06/15.
	// Copyright (c) 2015 dooZ. All rights reserved.
	//

	import Foundation

	import Darwin

	enum Signal: Int32 {
	case HUP = 1
	case INT = 2
	case QUIT = 3
	case ABRT = 6
	case KILL = 9
	case ALRM = 14
	case TERM = 15


	// known-good: Xcode 8, Swift 3

	import Foundation

	var standardError = FileHandle.standardError

	extension FileHandle : TextOutputStream {
	public func write(_ string: String) {
	guard let data = string.data(using: .utf8) else { return }

	erase_sim:
	./reset_sim.sh 2>/dev/null; true