tclementdev

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

hellerbarde

Latency numbers every programmer should know

L1 cache reference ......................... 0.5 ns
Branch mispredict ............................ 5 ns
L2 cache reference ........................... 7 ns
Mutex lock/unlock ........................... 25 ns
Main memory reference ...................... 100 ns             
Compress 1K bytes with Zippy ............. 3,000 ns  =   3 µs
Send 2K bytes over 1 Gbps network ....... 20,000 ns  =  20 µs
SSD random read ........................ 150,000 ns  = 150 µs

Read 1 MB sequentially from memory ..... 250,000 ns = 250 µs

jacobbubu

mr	Marathi
bs	Bosnian
ee_TG	Ewe (Togo)
ms	Malay
kam_KE	Kamba (Kenya)
mt	Maltese
ha	Hausa
es_HN	Spanish (Honduras)
ml_IN	Malayalam (India)
ro_MD	Romanian (Moldova)

pksunkara

[user]
	name = Pavan Kumar Sunkara
	email = pavan.sss1991@gmail.com
	username = pksunkara
[init]
	defaultBranch = master
[core]
	editor = nvim
	whitespace = fix,-indent-with-non-tab,trailing-space,cr-at-eol
	pager = delta

dergachev

OS X Screencast to animated GIF

This gist shows how to create a GIF screencast using only free OS X tools: QuickTime, ffmpeg, and gifsicle.

Instructions

To capture the video (filesize: 19MB), using the free "QuickTime Player" application:

ddunbar

New Build System Tricks

Command Line

alias xcbuild=$(xcode-select -p)/../SharedFrameworks/XCBuild.framework/Versions/A/Support/xcbuild
# THIS DOESNT WORK YET: xcbuild openIDEConsole  # … then switch to Xcode ➡️
xcbuild showSpecs
xcbuild build <foo.pif> [—target <target>]

DejanEnspyra

//
//  Obfuscator.swift
//
//  Created by Dejan Atanasov on 2017-05-31.
//

import Foundation

class Obfuscator: AnyObject {
    

kayoslab

### Global configuration

# Enable rules which are not in the default set
opt_in_rules:
  #  - anyobject_protocol                             # Prefer using `AnyObject` over `class` for class-only protocols.
  #  - array_init                                        # Prefer using `Array(seq)` over `seq.map { $0 }` to convert a sequence into an Array.
  #  - attributes                                        # Attributes should be on their own lines in functions and types, but on the same line as variables and imports.
  - block_based_kvo                                   # Prefer the new block based KVO API with keypaths when using Swift 3.2 or later.
  - class_delegate_protocol                           # Delegate protocols should be class-only so they can be weakly referenced.
  - closing_brace                                     # Closing brace with closing parenthesis should not have any whitespaces in the middle.

tomchristie

Visa requirements for UK conferences.

First you'll want to check if you need a visa to enter the UK.

• Nationals of the EU, Switzerland, and EEA countries will not need a visa, and are free to work and conduct business in the UK.
• Nationals from some designated countries such as USA may travel for tourist or business purposes under a visa exemption. The link above will detail what documents you need to provide in order to travel under a visa exemption.
• Other nationals will need a visa.

The rules for allowable business travel under a visa exemption are covered by the same rules as those travelling under a vistor visa. If you will be travelling under a visa-exemption and the conference is covering your costs in any way you should make sure to read the relevant section below.

VojtaStavik

import UIKit

class ViewController: UIViewController, UITableViewDelegate, UITableViewDataSource {

  @IBOutlet weak var tableView: UITableView!

  override func viewDidLoad() {
    super.viewDidLoad()
    NSLayoutConstraint.activate([
      tableView.topAnchor.constraint(equalTo: view.topAnchor),