Aron Cedercrantz rastersize

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

DEPRECATED for Xcode 10 🎈

(check out What's New in Swift at 11:40, slide 42)

Whole Module Compilation Optimizations: Why these terms are sometimes misleading

When you look up how to compile swift faster for debug builds, people very earnestly give advice that seems contradictory: you should "try using the whole module optimization flag," and also "never use whole module optimization for debugging". [^1]

This is confusing because some of us are using these two general words:

compilation: "turning text into an executable program"

Falsehoods programmers believe about time

This is a compiled list of falsehoods programmers tend to believe about working with time.

Don't re-invent a date time library yourself. If you think you understand everything about time, you're probably doing it wrong.

Falsehoods

There are always 24 hours in a day.
February is always 28 days long.
Any 24-hour period will always begin and end in the same day (or week, or month).

	#!/usr/bin/env xcrun --sdk macosx swift

	import Foundation

	enum Configuration: String {
	case debug = "Debug"
	case release = "Release"
	}

	// Get Info.plist path

	//
	// UIAccessorizedTextField.swift
	// AccessorizedTextField
	//
	// Created by Damien Laughton on 28/03/2018.
	// 2018 Mobilology Limited. No rights reserved.
	//

	import Foundation
	import UIKit

	import Foundation

	protocol Channel: IteratorProtocol {
	func send(_ value: Element?)
	}

	/// A blocking channel for sending values.
	///
	/// `send` and `receive` must run in separate separate execution contexts, otherwise you get a deadlock.
	final class BlockingChannel<A>: Channel {

	#!/usr/bin/env bash
	<% for type in types.classes { -%>
	<%_ if type.attributes["final"] != nil \|\| type.attributes["open"] != nil \|\| types.based[type.name]?.isEmpty == false { continue } -%>
	<%_ _%>git grep -lz 'class <%= type.name %>' \| xargs -0 perl -i'' -pE "s/class <%= type.name %>(?=\s\|:)/final class <%= type.name %>/g"
	<% } %>

	As of iOS 11/macOS High Sierra, and only including ones in Foundation and CoreFoundation

	Strings:

	_NSCFString - a CFStringRef or CFMutableStringRef. This is the most common type of string object currently.
	- May have 8 bit (ASCII) or 16 bit (UTF-16) backing store
	_NSCFConstantString - a compile time constant CFStringRef, like you'd get with @"foo"
	- May also be generated by dynamic string creation if matches a string in a pre-baked table of common strings called the StringROM
	NSBigMutableString - an NSString backed by a CFStorage (https://github.com/opensource-apple/CF/blob/master/CFStorage.h) for faster handling of very large strings
	NSCheapMutableString - a very limited NSMutableString that allows for zero-copy initialization. Used in NSFileManager for temporarily wrapping stack buffers.

	import Foundation

	// Alternatives to `Scanner` (before: `NSScanner`).


	// A scanner only needs a way to peek and to move to the next token.
	protocol ScannerProtocol {
	associatedtype Token: Equatable
	var peek: Token? { get }
	mutating func moveToNextToken()

	import Foundation
	final class Sample: NSObject {
	@objc dynamic var name: String = ""
	}

	class MyObj: NSObject {
	@objc dynamic var test: String = ""
	}

	extension NSObjectProtocol where Self: NSObject {