Enrique Garcia kikeenrique

Debugging the Swift Toolchain

Use these steps to debug components of the Swift toolchain. This allows you to see Swift's source code from the debugger – instead of disassembly. The debugger can also provide some variable names and values. This has been initially tested with libswiftCore.dylib.

These instructions were updated as of Swift 5.2.1.

Prerequisites

Edit Feb 4 5:16 PM: Skip to the bottom if you just want the article

It has been brought to my attention that rehosting someone else's content without asking them — even if you link to the original content — is not exactly polite. I did not ask the author before I rehosted his article, and while I feel I should have known better than to that, it just didn't occurr to me. It's not exactly plagarism, but it's still wrong on some level. I have reached out to him now about hosting it here publically, and if he says it's alright, I'll put it back.

You can find the original article here, on his site, and on his Medium page.

If you work on a Swift project that follows the Model-View-ViewModel (MVVM) architecture or similar, you may want to jump to counterpart in Xcode from your view to your model, and then to your view model. (ie. by using Ctrl+Cmd+Up and Ctrl+Cmd+Down).

You can do this in recent versions of Xcode by setting a configuration default.

From a terminal, just type this command and press Enter:

defaults write com.apple.dt.Xcode IDEAdditionalCounterpartSuffixes -array-add "ViewModel" "View"

My Time Machine Notes

Migration from External HDD to Samba

Create Samba share using a combination of the following references:
1. https://kirb.me/2018/03/24/using-samba-as-a-time-machine-network-server.html
2. https://www.reddit.com/r/homelab/comments/83vkaz/howto_make_time_machine_backups_on_a_samba/
Reviewed the following references for ideas on how to migrate Time Machine backups from external HDD to Time Capsule:
https://jason-townsend.blogspot.com/2008/08/how-to-transfer-local-time-machine.html

Diff output of two lldb commands

Setup

Copy the contents of the last snippet (lldbinit) from the gist page, and paste into your .lldbinit file. This makes the ksdiff macro known inside lldb.
Put file ksdiff.py in ~/.lldb/
sudo pip install temp
Restart Xcode debug session

Example

(lldb) ksdiff ;

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

	// Run any SwiftUI view as a Mac app.

	import Cocoa
	import SwiftUI

	NSApplication.shared.run {
	VStack {
	Text("Hello, World")
	.padding()
	.background(Capsule().fill(Color.blue))

	import Cocoa

	#if canImport(SwiftUI) && DEBUG
	import SwiftUI
	struct NSViewControllerPreview<ViewController: NSViewController>: NSViewControllerRepresentable {

	let viewController: ViewController

	init(_ builder: @escaping () -> ViewController) {
	viewController = builder()

	addmedia
	addphoto
	addvideo
	appinfo
	boot
	bootstatus
	clone
	create
	darwinup
	delete

	extension URLRequest {
	private func quote(_ string: String) -> String {
	// handle all the regular escape sequences
	var text = string.replacingOccurrences(of: "\\", with: "\\\\")
	text = text.replacingOccurrences(of: "\"", with: "\\\"")
	text = text.replacingOccurrences(of: "\n", with: "\\\n")
	text = text.replacingOccurrences(of: "\r", with: "\\\r")
	text = text.replacingOccurrences(of: "\t", with: "\\\t")
	return "\"\(text)\""
	}