const app = {
lines: document.getElementById('lines'),
textbox: createTextbox(),
lineTemplate: createLineTemplate(),
}

const socket = connect(
`ws://${location.host}/app`,
{

initial({ lines, uuid, charLimit }) {
app.uuid = uuid
app.charLimit = charLimit
lines.forEach(addLine)
},

added(line) {
addLine(line)
},

removed(i) {
app.lines.children[i].remove()
},

server.onclose = (ws) => {
if (ws.line) {
const i = lines.indexOf(ws.line)
lines.splice(i, 1)
server.sendToAll({ removed: i })
}
}

server.commands = {

begin(ws) {
const line = {
hash: ws.hash,
uuid: ws.uuid,
text: '',
}

ws.line = line
lines.push(line)
server.sendToAll({ added: line })
},

run() {
console.log(`Running on port ${this.port}`)

this.wss = new WebSocket.Server({
port: this.port,
verifyClient: this.verify.bind(this)
})

setInterval(
this.prune.bind(this),
this.pruneInterval * 1000
)

this.wss.on(
'connection',
this.connection.bind(this)
)
}

Steven Degutis

Full-stack software developer for hire

ObjC equivalents to Swift solutions #2: Avoiding ObjC method name collisions

April 19, 2017

When we created the Xcode project for our first iPhone app, Accomplish ("the quickest & easiest todo list app"), we had to choose a language to use: Swift or Objective-C. Our first blog post details why we chose Objective-C, despite the huge popularity of Swift in the past few years.

But Swift was created because Objective-C had some flaws. One of these is avoiding class name collisions without the use of prefixing, which our second blog post covers. Now we'll look at avoiding method name collisions.

The problem is that we might accidentally create a method in a subclass, with the same name as a private method in one of our superclasses. The compiler can't warn us about this because they're not forward-declared like public methods are.

One of the most common classes you'll subclass is UIViewController, so let's take a look at its private methods. Let's print all their methods at runtime:

#import <objc/runtime.h>

unsigned int count;
Method* methods = class_copyMethodList([UIViewController class], &count);

qsort_b(methods,
        count,
        sizeof(Method),
        ^int(const void* a, const void* b) {
            return strcmp(sel_getName(method_getName(*((Method*)a))),
                          sel_getName(method_getName(*((Method*)b))));
        });

for (int i = 0; i < count; i++) {
    const char* n = sel_getName(method_getName(methods[i]));
    NSLog(@"%s", n);
}

free(methods); // avoid memory leaks

Looks like about 60% of the methods start with at least one _. This adds up, since Apple explicitly says they're the only ones allowed to start method or class names with underscores. So even if we wanted to use that as our solution, we can't.

Most of the remaining method names are public methods we recognize from either UIViewController or one of its superclasses, like setView:, autorelease, setTitle:, setValue:forKey:, and viewIfLoaded.

But many of them don't appear anywhere in the public method list! Some of these we wouldn't have any need for, like containmentSupport, but some of them we might imagine using for our own private methods, like customTransitioningView or defaultPNGName.

Well at least this proves that there is a real danger here. But first let's see if we're overreacting, maybe the runtime warns us right away like it did with class name collisions. So let's take one of the more vital-looking private methods with an easy-to-guess signature:

- (void) _doCommonSetup {
    NSLog(@"craptastic.");
}

Put that in a UIViewController subclass and watch the console prove that it is called by the system even though it's our version and not the original implementation. (This will happen when you override any private method, whether it starts with an underscore or not.)

So how can we solve it?

One solution is to use a prefix for all your own methods. Notice that none of the internal methods contain '_' after the initial characters. Which means you can safely get away with using x_ as your prefix. So - (void) x_updateSomething; should always be safe.

But it's not future-proof. Just because Apple isn't using that now, doesn't mean they won't in the future. After all, they're already using non-underscore-prefixed names right now, which they really ought not to be doing in the first place.

If you want to get super-safe, you can use your own name as a prefix: - (void) penpapersw_updateSomething;. Personally I think this is a bit overkill. And even though it's safer, we can do one better:

Static functions. This is the safest, because unlike with regular C functions or Objective-C methods, when you define a static function, its name doesn't even exist at the point when it's time worry about name clashes. At compile-time, it literally becomes an "anonymous" function of sorts. In fact you can have two static functions with the same name in two different .m files in your own project, and there's still no danger of name collision!

static void UpdateSomething(MyViewController* self, NSString* thing) {
    self.thing = [thing uppercaseString];
}

If you use static functions, keep in mind that even if you define it inside the body of the Objective-C class implementation, they still don't have access to any properties or ivars. So you'll still have to pass self as the first parameter, or at least whatever relevant data & objects it needs access to.

One thing to keep in mind is that when you start typing the type names of parameters in your static function definitions, Xcode doesn't even try to auto-complete them, so you have to type them out fully, which gets real old real fast once you've gotten used to auto-completion everywhere else.

There's one other solution, but it's pretty ridiculous: create a helper function that scours through all your own subclasses and their methods at runtime, and prints a list of all the methods you've overridden, minus the ones you've already "approved" (like viewDidLoad). This would be really tricky to get right while still being low-maintenance, so I'm not even going to give example code.

Phew! Now we have several solutions for avoiding accidentally overriding an important private method from within our subclass.

About me

My name is Steven Degutis, and I've been writing software professionally for almost a decade. During that time, I've written many apps and websites, quite a few techical articles, and kept up-to-date with the rapidly evolving software industry.

If you have software needs for web, mobile, or desktop, and are looking for a seasoned software professional, please reach out to me at sbdegutis@gmail.com to set up a phone call.

Work Experience

  • Self-employed – present
  • Clean Coders – 5 years
  • 8th Light – 2 years
  • Big Nerd Ranch – 1 year
  • Self-employed - 1 year

Platforms

  • Web: full-stack
  • iOS (UIKit)
  • macOS (Cocoa)
  • REST APIs
  • AWS / EC2 / ELB

Languages

  • JavaScript
  • HTML5 / CSS
  • Swift
  • Objective-C
  • Clojure

Frameworks

  • Node.js
  • Express.js
  • React
  • Vue.js
  • Electron

Technical articles

Over the past decade, I've written a total of 169 technical articles on various programming languages, frameworks, best practices, and my own projects, as I kept up-to-date and active in the software industry.

Subscribe via RSS / Atom.

Chronological

Portfolio

Here are some of the projects I'm most proud of. They were created using a variety of technologies, running on several different platforms and OSes. They're all finished products, and many of them are open source.

CleanCoders.com

Website - Online Video Store

I wrote this web store for Robert "Uncle Bob" Martin, using Clojure for the back-end, and JavaScript for the front-end. Over the course of 5 years, I took the site from a simple three-page website to a full enterprise-ready business solution, with nearly 100% test coverage.

  • Clojure
  • Datomic
  • jQuery / D3.js
  • JavaScript
  • ClojureScript

Docks

macOS app - Dock Utility

I made Docks in 2009 for users who wanted to swap out icons in their Dock with a single click. Its unique functionality and design aesthetic attracted the attention of Apple, Engadget, MacWorld, and led to an acquisition of my start-up by Big Nerd Ranch.

  • Apple.com Staff Pick
  • MacWorld 4/5 Rating
  • MacWorld Gem of the Year
  • Featured on Engadget.com

Leviathan

macOS app - Clojure IDE

Source Code

While working on CleanCoders.com, a website written completely in Clojure, I increased my productivity by building a custom IDE for macOS designed specifically for Clojure projects.

  • Objective-C
  • Clojure
  • C / C++
  • Cocoa
  • Themeable

Zephyros

macOS app - Hackable Automation

Source Code

This began as an experiment to see how many languages I could use to script a custom macOS window manager using our custom TCP protocol. Eventually it had bindings for Clojure, Ruby, Python, Go, JavaScript, CoffeeScript, Node.js, Chicken Sceme, and Racket, as well as other community additions.

  • TCP / Unix sockets
  • Custom protocol
  • Highly Scriptable
  • 10+ language bindings
  • Open source community

Bubble Maker

iOS app - Bubble simulator

This toy was made in a weekend to entertain my 1 year old daughter. It lets you create bubbles with your fingers, which then simulate physics by bumping into each other and falling.

  • SpirteKit
  • Custom art
  • Physics simulation
  • iOS
  • tvOS

Quick List

iOS app - Todo list app

When I couldn't find an app in the App Store that let me make very simple lists extremely quickly, I made one myself. I use it almost every day to organize and track my activities.

  • In-app purchases
  • Custom UI / UX
  • Social media
  • App Store artwork
  • Spring animations

sdegutis.com

Website - Personal Portfolio

Source Code

This very site itself was written from scratch in about a day. It uses best practices for modern responsive web design, and a custom build phase to compile the sources into a single HTML file.

  • Node.js
  • Pug / Jade
  • LessCSS
  • HTML5
  • WebSockets

2048

Java app - Game

Source Code

The game 2048 (created by Gabriele Cirulli) is so fun that my kids wanted their own copy. So I wrote this version in Java 8, using JavaFx for attractive graphics and silky smooth animations.

  • Java 8
  • JavaFx
  • Modular code
  • Customizable
  • Animations

Mjolnir

macOS app - Window Manager

Source Code

I created this app to increase my productivity by letting me move windows around in macOS using keyboard shortcuts. It grew into a community-driven highly extensible app, using Lua for its plugin system.

  • Objective-C
  • Embedded Lua
  • Plugin system
  • Fully documented
  • 5,000 GitHub stars

AffluentConfidante.com

Website - Social Network

Implementing this elite social network gave me experience integrating both Apple Pay and credit card payments (via Stripe.com) seamlessly into web apps, for a frictionless and pain-free payment experience.

  • Clojure
  • Elastic Beanstalk
  • PostgreSQL
  • Stripe.com
  • Apple Pay

HyperChat

Website - Live Chatroom

Source Code

This isn't just any chatroom. In this web app, you can see what everyone is typing while they type it. I made this in order to scratch my itch for making real-time apps and games, and learned how to use WebSockets in the process.

  • JavaScript
  • WebSockets
  • Node.js
  • Vue.js
  • CSS

Bahamut

macOS app - Music Player

Source Code

As iTunes went through many user interface changes, I wanted an app that was consistent, intuitive, and easy to use. So I created Bahamut, a minimal music player for macOS with a custom user interface.

  • Objective-C
  • Custom UI
  • Cocoa
  • Core Data
  • AVFoundation

Chatter

macOS app - Chat (IRC) Client

Source Code

This was written in 2009, before the time of Slack, when IRC was the main way for programmers to get short-term assistance from each other. Its purpose was to be a beautiful app with an emphasis on simplicity and usability over technical power.

  • Async networking
  • Core Animation
  • Core Text
  • IRC Protocol
  • UI Design

AppGrid

macOS app - Window Manager

Source Code

This is an app I actually use every single day. It lets you move windows with global keyboard shortcuts. Since it uses Vim-like key bindings, it should feel pretty natural to any programmer. There's no configuration needed; it Just Works™.

  • Minimalist UI
  • Simple UI
  • Vim-like Hotkeys
  • Global Hotkeys
  • Zero-configuration

Hydra

macOS app - Lua window manager

Source Code

As an evolution of Phoenix, Hydra was my first attempt at embedding a full Lua virtual machine into an Objective-C app, to make a lightweight and efficient window manager that focused on speed, low memory usage, low CPU usage, and overall being gentle on laptop batteries.

  • Embedded Lua
  • Generated docs
  • Lightweight
  • Memory efficient
  • CPU efficient

Phoenix

macOS app - JavaScript window manager

Source Code

As an evolution of Zephyros, Phoenix was my attempt to use Cocoa's native JavaScript bindings to make a more lightweight and efficient window manager, that focused on speed, low memory usage, low CPU usage, and overall being gentle on laptop batteries.

  • JavaScriptCore
  • JavaScript API
  • Lightweight
  • Memory efficient
  • CPU efficient

Smaller projects

These may be tiny, but they're interesting technical feats.

Lua4SwiftSwift framework for embedding Lua with a native Swift API.
chooseCommand line fuzzy-matching tool for macOS that uses a GUI
musicCommand line music daemon for macOS that only speaks JSON
hectoCommand line text editor with an embedded Lua plugin system
ZephSharpWindow manager for Windows using Clojure for scripting
managementMinimalist EC2 configuration & deployment tool in Ruby.
go.assertAssertion helper package for writing tests in Go.
go.shattrGo library for printing shell-attributed strings to stdout.
OCDSpec2Objective-C based testing framework with Xcode integration.