Rodrigo Cardoso Buske Robuske

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

	# Was asked how I keep my zshrc config sync'd between my computers with Dropbox

	# Add a new directory in your Dropbox (or use an existing one)
	mkdir -p ~/Dropbox/ohmyzsh

	# move existing file to Dropbox
	mv ~/.zshrc ~/Dropbox/ohmyzsh/zshrc

	# symlink file back to your local directory
	ln -s ~/Dropbox/ohmyzsh/zshrc ~/.zshrc

	# 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)

	#!/bin/bash

	echo "Removing unavailable simulators..."
	xcrun simctl delete unavailable

	echo "Brew cleanup..."
	brew cleanup

	echo "Removing Xcode Caches..."
	rm -rf ~/Library/Caches/com.apple.dt.Xcode

	// How to:
	// 1. Open the Firebase Analytics Dashboard
	// 2. Scroll to bottom, where you see the "Users by Device model" widget
	// 3. Click "View device models" in that widget (this opens the "Tech details" Firebase Analytics page)
	// 4. Above the table shown in the new page, click on the “Device model” drop down menu and select “OS with Version”
	// 5. Make sure to select “OS with version” and not “OS Version”
	// 6. On the top right corner of the page, click on the “Share this report” icon (next to the date)
	// 7. Click “Download file” on the new side bar, then “Download CSV"
	// 8. Open the file and select the iOS/Android breakdown raw data
	// 9. Replace the sample data in this script with your data

	//
	// MRDMenuView.h
	// MobileRadio
	//
	// Created by Steven Troughton-Smith on 29/02/2020.
	// Copyright © 2020 High Caffeine Content. All rights reserved.
	//

	#import <UIKit/UIKit.h>

	//
	// PSTLDraggableColorSwatchView.h
	// Pastel
	//
	// Created by Steven Troughton-Smith on 06/03/2020.
	// Copyright © 2020 Steven Troughton-Smith. All rights reserved.
	//

	@import UIKit;

	struct User: Equatable {
	var firstName: String
	var lastName: String
	}

	@main
	struct MyApp: App {
	@State var value = User(firstName: "", lastName: "")
	@State var showEdit = false