Mykhailo mpashnyov

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,

Greetings and salutations, NSHipsters!

As the year winds down, it's a tradition here at NSHipster to ask you, dear readers, to offer up your favorite tricks and tips from the past year as gifts to your fellow hipsters. With iOS 9, El Capitan, brand new watch- and tvOS's, and the open-sourcing of some minor Apple-related tech, there's bound to be lots to share.

Submit your favorite piece of Swift or @objc trivia, helpful hints, unexpected discoveries, useful workarounds, useless fascinations, or anything else you found cool this year. Just comment below!

If you need inspiration, try [the list from last year][2015], or [from the year before][2014], or [from the year before that][2013].

This gist outlines how to resize a view when a keyboard appears using Auto Layout (there are a bunch of code samples out there that manually adjust the view's frame, but that's just so 2013). The method I outline below works universally on both iPhone and iPad, portrait and landscape, and is pretty darn simple.

Setting Up

The first thing to do is to define our containing view controller, the view, and the bottom constraint that we'll use to adjust its size.

Here's HeightAdjustingViewController.h. We don't need to expose any public properties, so it's pretty bare.

Generate the list yourself:

$ cd /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS*.sdk/System/Library/Frameworks/UIKit.framework/Headers
$ grep UI_APPEARANCE_SELECTOR ./*     | \
  sed 's/NS_AVAILABLE_IOS(.*)//g'     | \
  sed 's/NS_DEPRECATED_IOS(.*)//g'    | \
  sed 's/API_AVAILABLE(.*)//g'        | \
  sed 's/API_UNAVAILABLE(.*)//g'      | \
 sed 's/UI_APPEARANCE_SELECTOR//g' | \

	// MIT License
	//
	// Copyright (c) 2018 Joom
	//
	// Permission is hereby granted, free of charge, to any person obtaining a copy
	// of this software and associated documentation files (the "Software"), to deal
	// in the Software without restriction, including without limitation the rights
	// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
	// copies of the Software, and to permit persons to whom the Software is
	// furnished to do so, subject to the following conditions:

	let a: Double? = 1.0
	let b: Double? = 2.0
	let c: Double? = 3.0
	let d: Double? = 4.0
	let e: Double? = 5.0
	let f: Double? = 6.0
	let g: Double? = 7.0

	extension Optional {
	func `or`(_ value : Wrapped?) -> Optional {

	//
	// SpinlockTestTests.swift
	// SpinlockTestTests
	//
	// Created by Peter Steinberger on 04/10/2016.
	// Copyright © 2016 PSPDFKit GmbH. All rights reserved.
	//

	import XCTest

	#!/bin/bash
	killall Xcode
	xcrun -k
	xcodebuild -alltargets clean
	rm -rf "$(getconf DARWIN_USER_CACHE_DIR)/org.llvm.clang/ModuleCache"
	rm -rf "$(getconf DARWIN_USER_CACHE_DIR)/org.llvm.clang.$(whoami)/ModuleCache"
	rm -rf ~/Library/Developer/Xcode/DerivedData/*
	rm -rf ~/Library/Caches/com.apple.dt.Xcode/*
	open /Applications/Xcode.app

	NS_INLINE NSRange NSRangeMake(NSUInteger loc, NSUInteger len) {
	return NSMakeRange(loc, len);
	}

	NS_INLINE NSUInteger NSRangeMax(NSRange range) {
	return NSMaxRange(range);
	}

	NS_INLINE BOOL NSRangeContainsLocation(NSUInteger loc, NSRange range) {
	return NSLocationInRange(loc, range);

	[db makeFunctionNamed:@"UTTypeConformsTo" maximumArguments:2 withBlock:^(sqlite3_context context, int argc, sqlite3_value *argv) {
	if (sqlite3_value_type(argv[0]) == SQLITE_TEXT) {

	const unsigned char *a = sqlite3_value_text(argv[0]);
	const unsigned char *b = sqlite3_value_text(argv[1]);

	CFStringRef as = CFStringCreateWithCString(0x00, (const char*)a, kCFStringEncodingUTF8);
	CFStringRef bs = CFStringCreateWithCString(0x00, (const char*)b, kCFStringEncodingUTF8);

	sqlite3_result_int(context, UTTypeConformsTo(as, bs));