Sam Lu senmu

If you work on a Swift project that follows the Model-View-ViewModel (MVVM) architecture or similar, you may want to jump to counterpart in Xcode from your view to your model, and then to your view model. (ie. by using Ctrl+Cmd+Up and Ctrl+Cmd+Down).

You can do this in recent versions of Xcode by setting a configuration default.

From a terminal, just type this command and press Enter:

defaults write com.apple.dt.Xcode IDEAdditionalCounterpartSuffixes -array-add "ViewModel" "View"

libdispatch efficiency tips

The libdispatch is one of the most misused API due to the way it was presented to us when it was introduced and for many years after that, and due to the confusing documentation and API. This page is a compilation of important things to know if you're going to use this library. Many references are available at the end of this document pointing to comments from Apple's very own libdispatch maintainer (Pierre Habouzit).

My take-aways are:

You should create very few, long-lived, well-defined queues. These queues should be seen as execution contexts in your program (gui, background work, ...) that benefit from executing in parallel. An important thing to note is that if these queues are all active at once, you will get as many threads running. In most apps, you probably do not need to create more than 3 or 4 queues.
Go serial first, and as you find performance bottle necks, measure why, and if concurrency helps, apply with care, always validating under system pressure. Reuse

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,

	//
	// SegmentedControlNavBar.swift
	//
	// Navigation bar with a segmented control in SwiftUI.
	//
	// Created by Magnus W. Solbakken on 18/05/2020.
	// Copyright © 2020 Magnus W. Solbakken.
	//

	import SwiftUI

	struct Contact: Decodable, CustomStringConvertible {
	var id: String
	@NestedKey
	var firstname: String
	@NestedKey
	var lastname: String
	@NestedKey
	var address: String

	enum CodingKeys: String, NestableCodingKey {

	#!/usr/bin/swift sh
	import Foundation
	import PromiseKit // @mxcl ~> 6.5
	import Swifter // @mattdonnelly == b27a89

	let swifter = Swifter(
	consumerKey: "FILL",
	consumerSecret: "ME",
	oauthToken: "IN",
	oauthTokenSecret: "https://developer.twitter.com/en/docs/basics/apps/overview.html"

	extension UIView {
	@objc func exerciseAmbiguityInLayoutRepeatedly() {
	if self.hasAmbiguousLayout {
	Timer.scheduledTimer(timeInterval: 0.5,
	target: self,
	selector: #selector(UIView.exerciseAmbiguityInLayout),
	userInfo: nil,
	repeats: true)
	}
	}

	#!/bin/bash

	set -e

	CONTENTS=$(tesseract -c language_model_penalty_non_dict_word=0.8 --tessdata-dir /usr/local/share/tessdata/ "$1" stdout -l eng \| xml esc)

	hex=$((cat <<EOF
	<?xml version="1.0" encoding="UTF-8"?>
	<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
	<plist version="1.0">

	#!/bin/bash

	ITERATION=1
	EXTENSION="mp4"
	FILENAME="$HOME/Desktop/Simulator Recording.$EXTENSION"

	while [ -e "$FILENAME" ]
	do
	ITERATION=$((ITERATION+1))
	FILENAME="$HOME/Desktop/Simulator Recording $ITERATION.$EXTENSION"

	# 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)