Steve Thompson philosopherdog

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

XML GET

curl -H "Accept: application/xml" -H "Content-Type: application/xml" -X GET "http://hostname/resource"

JSON GET

curl -i -H "Accept: application/json" -H "Content-Type: application/json" -X GET "http://hostname/resource"

JSON PUT

(NOTE: Current and future versions of this and any other Advantage 2-related things I post will be at https://github.com/nicholasknight/adv2keyboard)

I received my Advantage 2 today. There's no full manual yet, even though keyboards are apparently arriving (hint, hint, Kinesis). The quick start guide leaves out the "power user mode", and there are some other quirks.

Update: A manual has been posted at http://www.kinesis-ergo.com/advantage2-resources/

It includes a dictionary for the key maps, but I know it leaves at least one possible key undocumented: it does not list f14, but I have successfully mapped my scrollock to f14 regardless.

It also mentions a firmware version (1.0.18) that doesn't seem to be available yet, with a new feature (status report playback speed).

Declaring models

class Dog: Object {

  dynamic var id = ""

  dynamic var name = ""

 dynamic var tempVariable = ""

	extension UIView {

	// MARK: - Safe anchors

	/// Contains view's top anchor depending to iOS version.
	var safeTopAnchor: NSLayoutYAxisAnchor {
	if #available(iOS 11.0, *) {
	return self.safeAreaLayoutGuide.topAnchor
	} else {
	return self.topAnchor

	import Darwin

	@dynamicMemberLookup
	struct Environment {
	subscript(dynamicMember name: String) -> String? {
	get {
	guard let value = getenv(name) else { return nil }

	return String(validatingUTF8: value)
	}

	// The MIT License (MIT)
	//
	// Copyright (c) 2017 Alexander Grebenyuk (github.com/kean).

	import Foundation
	import RxSwift
	import RxCocoa


	extension ObservableType {

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

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

	extension NSObjectProtocol where Self: NSObject {

	/* We call layoutIfNeeded() immediately after reloadData()
	* to force collection view to perform layout immediately
	* This is required to let the setContentOffset() in dispatch block to be executed
	* after collection view has completed performing its layout to scroll to the correct offset
	* For further explanations, please see: http://goo.gl/BpzlA5 and http://goo.gl/6CH64b
	*/
	self.collectionView.reloadData()
	self.collectionView.layoutIfNeeded()

	dispatch_async(dispatch_get_main_queue(), {

	# Xcode
	#
	# gitignore contributors: remember to update Global/Xcode.gitignore, Objective-C.gitignore & Swift.gitignore

	## Build generated
	build/
	DerivedData/

	## Various settings
	*.pbxuser