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@tclementdev
tclementdev / libdispatch-efficiency-tips.md
Last active September 20, 2025 20:31
Making efficient use of the libdispatch (GCD)

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

@douglashill
douglashill / LocalisedStrings.swift
Last active September 17, 2018 09:02
Generating an enum to ensure only defined localised string keys are used. For development on Apple platforms.
// Douglas Hill, February 2018
import Foundation
/// Returns a localised string with the key as an enum case so the compiler checks it exists.
/// The enum should be automatically generated using UpdateLocalisedStringKeys.swift.
public func localisedString(_ key: LocalisedStringKey) -> String {
return Bundle.main.localizedString(forKey: key.rawValue, value: nil, table: nil)
}
@oliveratgithub
oliveratgithub / emojis.json
Last active August 24, 2025 16:17
Emoji-list with emojis, names, shortcodes, unicode and html entities [massive list]
{
"emojis": [
{"emoji": "👩‍👩‍👧‍👧", "name": "family: woman, woman, girl, girl", "shortname": ":woman_woman_girl_girl:", "unicode": "1F469 200D 1F469 200D 1F467 200D 1F467", "html": "👩‍👩‍👧‍👧", "category": "People & Body (family)", "order": ""},
{"emoji": "👩‍👩‍👧‍👦", "name": "family: woman, woman, girl, boy", "shortname": ":woman_woman_girl_boy:", "unicode": "1F469 200D 1F469 200D 1F467 200D 1F466", "html": "👩‍👩‍👧‍👦", "category": "People & Body (family)", "order": ""},
{"emoji": "👩‍👩‍👦‍👦", "name": "family: woman, woman, boy, boy", "shortname": ":woman_woman_boy_boy:", "unicode": "1F469 200D 1F469 200D 1F466 200D 1F466", "html": "👩‍👩‍👦‍👦", "category": "People & Body (family)", "order": ""},
{"emoji": "👨‍👩‍👧‍👧", "name": "family: man, woman, girl, girl", "shortname": ":man_woman_girl_girl:", "unicode": "1F468 200D 1F469 200D 1F467 200D 1F467", "html": "👨‍👩&z
@nyg
nyg / MemoryAddress.swift
Last active July 9, 2024 03:38
Get the memory address of both class and structure instances in Swift.
// https://stackoverflow.com/a/45777692/5536516
import Foundation
struct MemoryAddress<T>: CustomStringConvertible {
let intValue: Int
var description: String {
let length = 2 + 2 * MemoryLayout<UnsafeRawPointer>.size
class Logging(object):
__name__ = 'logger.info(1)'
plist = '/System/Library/Preferences/Logging/Subsystems/'
def __init__(__name__, plist, *args, **kwargs):
super(getLogger/, self).__init__()
logger.info('Input parameters:\n'
'accessibility: "{com.apple.Accessibility.plist}"\n'

FWIW: I (@rondy) am not the creator of the content shared here, which is an excerpt from Edmond Lau's book. I simply copied and pasted it from another location and saved it as a personal note, before it gained popularity on news.ycombinator.com. Unfortunately, I cannot recall the exact origin of the original source, nor was I able to find the author's name, so I am can't provide the appropriate credits.


Effective Engineer - Notes

What's an Effective Engineer?

@zwaldowski
zwaldowski / Extra Logging for My Great App.mobileconfig
Last active March 28, 2025 03:47
Apple Configuration Profile for Logging in iOS 10 and macOS Sierra
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<!-- iOS 10, macOS Sierra, and friends bring a new logging subsystem that's
supposed to scale from the kernel, up to frameworks, and up to apps. It defaults
to a more regimented, privacy-focused approach that large apps and complex
systems need.
It, along with Activity Tracing introduced in iOS 8 and macOS Yosemite and the
Console app in macOS Sierra, hope to help you graduate from caveman debugging to
@warpling
warpling / CircleBloom.h
Last active July 25, 2016 23:10
Circle Bloom!?
//
// CircleBloom.h
// Blackbox
//
// Created by Ryan McLeod on 7/25/16.
// Copyright © 2016 Ryan McLeod. All rights reserved.
//
#import <UIKit/UIKit.h>
@Ashton-W
Ashton-W / .lldbinit
Created April 19, 2016 04:27
LLDB sim_location command (lldbinit)
command alias sim_location expr (void)NSLog(@"Printing Simulator App Paths:\n\nBundle:\n%@\n\nDocuments:\n%@\n\n", [[NSBundle mainBundle] resourcePath], [[[[NSFileManager defaultManager] URLsForDirectory:NSDocumentDirectory inDomains:NSUserDomainMask] lastObject] resourceSpecifier]);
@warpling
warpling / CGRectGetCenter.h
Created April 2, 2016 23:09
CGRectGetCenter
#define CGRectGetCenter(rect) ({ __typeof__(rect) __r = (rect); (CGPoint) { CGRectGetMidX(__r), CGRectGetMidY(__r)}; })