rowwingman

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

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Automatic build versions from git in Xcode (and other goodies)

Installation procedure for pre-build actions to automatically populate Xcode Info.plist with dynamic data.

1. Xcode Scheme pre-action

Edit Xcode Scheme and add a pre-action script. Copy the contents of preaction.sh into the pre-action script box.

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ssh-keygen -t rsa -b 4096 -N '' -C "rthijssen@gmail.com" -f ~/.ssh/id_rsa
ssh-keygen -t rsa -b 4096 -N '' -C "rthijssen@gmail.com" -f ~/.ssh/github_rsa
ssh-keygen -t rsa -b 4096 -N '' -C "rthijssen@gmail.com" -f ~/.ssh/mozilla_rsa

rowwingman

//
//  GradientView.swift
//  Aura
//
//  Created by Egor Sakhabaev on 23.07.17.
//  Copyright © 2017 Egor Sakhabaev. All rights reserved.
//

import UIKit

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//
//  AsynchronousOperation.swift
//
//  Created by Vasily Ulianov on 09.02.17.
//  Copyright © 2017 Vasily Ulianov. All rights reserved.
//

import Foundation

/// Subclass of `Operation` that add support of asynchronous operations.

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import Foundation

/// An abstract class that makes building simple asynchronous operations easy.
/// Subclasses must implement `execute()` to perform any work and call
/// `finish()` when they are done. All `NSOperation` work will be handled
/// automatically.
open class AsynchronousOperation: Operation {

    // MARK: - Properties

rowwingman

What is a mutex and how does it work

Imagine a big office (your program), with many assets (shared resources) and many employees (threads). For example, all employees share one common resource - a toilet. They have agreed to use a label on a toilet's door (mutex).

When an employee wants to use the toilet he checks a label on a door (locks a mutex). If it is "engaged" he waits (blocks on a mutex), then when it is "free", he enters the toilet and changes the label to

rowwingman

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)

rowwingman

#########################
# .gitignore file for Xcode4 and Xcode5 Source projects
#
# Apple bugs, waiting for Apple to fix/respond:
#
#    15564624 - what does the xccheckout file in Xcode5 do? Where's the documentation?
#
# Version 2.3
# For latest version, see: http://stackoverflow.com/questions/49478/git-ignore-file-for-xcode-projects
#