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

JohnSundell

/**
 *  Perform a throwing expression, and throw a custom error in case the expression threw
 *
 *  - parameter expression: The expression to execute
 *  - parameter error: The custom error to throw instead of the expression's error
 *  - throws: The given error
 *  - returns: The return value of the given expression
 */
func perform<T>(_ expression: @autoclosure () throws -> T, orThrow errorExpression: @autoclosure () -> Error) throws -> T {
    do {

sgr-ksmt

extension DispatchQueue {
    class func mainSyncSafe(execute work: () -> Void) {
        if Thread.isMainThread {
            work()
        } else {
            DispatchQueue.main.sync(execute: work)
        }
    }

    class func mainSyncSafe<T>(execute work: () throws -> T) rethrows -> T {

steipete

# The trick is to link the DeviceSupport folder from the beta to the stable version.
# sudo needed if you run the Mac App Store version. Always download the dmg instead... you'll thank me later :)

# Support iOS 15 devices (Xcode 13.0) with Xcode 12.5:
sudo ln -s /Applications/Xcode-beta.app/Contents/Developer/Platforms/iPhoneOS.platform/DeviceSupport/15.0 /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/DeviceSupport

# Then restart Xcode and reconnect your devices. You will need to do that for every beta of future iOS versions

# (A similar approach works for older versions too, just change the version number after DeviceSupport)

krzyzanowskim

import Cocoa

// for-in
func checkForIn(array: [Int], dict: [Int: String]) {
    for num in array where dict[num] != nil {
        num
    }
}

checkForIn([1,2,3,4], dict: [1:"one", 2:"two"])

christophermark

What is "idle mode"?

Idle mode is a state where the phone has no network connectivity and apps are temporarily suspended. Idle mode gets triggered by one of two ways: an asleep, still, unplugged phone (Doze mode), and when an app has not been opened in a significant amount of time (App Standby Mode). During idle mode via Doze, the phone will wake up periodically for a short amount of time, allowing apps to run and use network connectivity. Using several different methods outlined below, it is possible to wake apps up during idle mode outside of these maintenance windows.

Time to enter Doze mode

1 hour of being still after the screen turns off.

Time to enter App Standby mode

TBD

Idle maintenance windows

feighter09

// MARK: - Swizzling
extension UIFont {
  class var defaultFontFamily: String { return "Georgia" }
  
  override public class func initialize()
  {
    if self == UIFont.self {
      swizzleSystemFont()
    }
  }

shyampurk

private static PreviewCallback previewCallback = new PreviewCallback() {

        /**
         * {@inheritDoc}
         */
        @Override
        public void onPreviewFrame(byte[] data, Camera cam) {
            if (data == null) throw new NullPointerException();
            Camera.Size size = cam.getParameters().getPreviewSize();
            if (size == null) throw new NullPointerException();

wearethefoos

#!/usr/bin/env bash
#
# Rails console script that can be run on AWS Elastic Beanstalk.
#
# Run this script from the app dir (/var/app/current) as root (sudo script/aws-console)
#

set -xe

EB_SCRIPT_DIR=$(/opt/elasticbeanstalk/bin/get-config container -k script_dir)

derjohng

#!/bin/sh
# Create a RAM disk with same perms as mountpoint
# Script based on http://itux.idev.pro/2012/04/iservice-speed-up-your-xcode-%D0%BD%D0%B5%D0%BA%D0%BE%D1%82%D0%BE%D1%80%D1%8B%D0%B5-%D1%81%D0%BF%D0%BE%D1%81%D0%BE%D0%B1%D1%8B/ with some additions
# Usage: sudo ./xcode_ramdisk.sh start

USERNAME=$(logname)

TMP_DIR="/private/tmp"
RUN_DIR="/var/run"