Emoji Tac Toe Opened Sourced

Happy Father’s Day!


To celebrate my 28th Father’s Day I’ve opened sourced Emoji Tac Toe. It’s actually not a big deal to anyone but me. It’s kinda of scary open sourcing code that you wrote alone and without first cleaning it up. But what the heck. If someone can learn something from this code, why keep it locked away. It’s already been on GitHub for a year. It’s not getting any prettier under lock and key.

You can find the source code at github.com/jpavley/Emoji-Tac-Toe2. And you can download the iOS app on the App Store at John Pavley > Emoji Tac Toe.

You can play Emoji Tac Toe on your iPhone, your iPad, and your Apple Watch. (As long as you are running iOS 9.3 or later.)

I guess I should chat a little bit about the code just in case you want to take a peek.


I plan on refactoring the code quite a bit. I want to basically refactor it so that the core is separate from the iOS implementation and I can port it easily to the web and to Android. Maybe Windows too. Who knowns! I’m going to start this process by adding unit tests and then by tearing it apart.


I plan on updating the code for iOS 11, including Swift 4 and ARKit. I’ve been meaning to add multiplayer over BlueTooth and MessageKit capabilities. I also want to complete the tvOS and macOS implementations.


The core code lives in the EmojiTicTacToe.swift file. Since there are more emoji than I can count I have cherry picked the 1100 that I wanted to include. This is still too many and I should cut it down further. It’s too many emoji because choosing which emoji to play with is difficult. I can’t use Apple’s keyboard user interface because I can’t restrict it to just showing emoji. And I don’t want to waste my time recreating Apple’s design. Also, this game is not about typing anything so a keyboard doesn’t make sense.

Instead I create an array of emoji and it works very well. iOS is great at dealing with Unicode.

Tic Tac Toe is an ancient game and simple. There only eight winning vectors. So, it’s easy to brute force and just check any board for the eight vectors.

As emoji are text it’s simple to translate a game board into a string and back. Interoperability with messaging and tweeting is free. This is why I love emoji! Rich graphics without the cost of image file management. Once day when operating systems allow custom emoji we’ll stop using PNGs and JPEGs altogether. On that day the web will be more fast and safe than ever!

Given the simplicity of the game, my AI is equally simple. When it’s the AI’s turn, I look for an open cell, look for a blocking move or look for a winning move using the eight winning vectors as my guide. Because tic tac toe is too easy to prevent absolute boredom I add a bit of random error into the AI’s thinking so that if the player is paying attention she can beat the machine.


ViewController.swift contains iPhone/iPad specific code.

I found I needed some iPad specific code to avoid a crash when presenting Apple’s standard share UIActivityViewController. I did not open a radar.

I handle several gestures that I’m sure my players never discover but they are there none the less:

  • A long press on an emoji can trigger an attack if battle mode is enabled. A few emoji will do cool tricks in battle mode. There are several battle mode strategy functions that implement these tricks. My favorite is youWin which lets the other player win.
  • Panning up and down turns sounds on and off. That should be a standard gesture for all games!
  • A shake starts are new game with a random pair of emoji. This is the best way to start a new game as choosing particular emoji is a pain.


NewGameViewController.swift contains the code for the game settings on the iPhone/iPad.

Originally, I had the iPhone and Watch Extension collaborate so that one could control the other. But the effort was not worth the reward. Now the two version are completely independent.

I use a UIPickerView with two components to enable the player to choose two emoji. It’s not bad at all if there were only 20 or 30 emoji. But it’s just too much spinning to find a particular emoji out of 1100!

If the user tries to choose the same emoji for player 1 and player 2 (or the AI) I detect that and have the UIPickerView jump to the next emoji. See ensureRowsAreUnique(component: row:).

To make finding a particular emoji a bit easier I allow the player to jump over groups of emoji in the UIPickerView by tapping on the labels for each player. I’m guessing nobody would ever find this feature but the labels are colored blue to indicate they buttons.


InterfaceController.swift contains the code for a very simple version of Emoji Tac Toe that runs on watchOS. I actually like this version if the game best. No battle mode, no sound, no popovers, no choice of emoji. Just a single player game you tap out on your watch while waiting for the train.

Programming the UI for watchOS reminded me of my VisualBasic days! Each button view has it own handler function. No way to aggregate the touches and dispatch them with a switch statement!

Final Notes

All-in-all this code is pretty rough and need a lot of work. But it does work and hardly ever crashes. So that’s something. There is a half-finished tvOS implementation but I’m going to rethink it so don’t look at it!

I had to delete the sound effect that I didn’t create myself. Your build of Emoji Tac Toe will not sound like mine. But otherwise you are free, within the MIT License constraints, to do what you like with the code.

Swift Programming: Filtering vs For Loops

The current version 3.1 has come a long way from the Yet-Another-C-Based-Syntax of the 1.0 version of Swift.

One of the best features of Swift is how functional programming idioms are integrated into the core of the language. Like JavaScript, you can code in Swift in several methodologies, including procedural, declarative, object-oriented, and functional. I find it’s best to use all of them all simultaneously! It’s easy to become a victim of the law of diminishing returns if you try to stick to one programming idiom. Swift is a very expressive coding language and it’s economical to use different styles for different tasks in your program.

This might be hard for non-coders to understand but coding style is critical for creating software that functions well because a good coding style makes the source easy to read and easy to work with. Sometimes you have to write obscure code for optimization purposes but most of the time you should err of the side of clarity.

Apple has made a few changes to Swift that help with readability in the long term but remove traditional C-based programming language syntax that old-time developers like me have become very attached to.

The most famous example was the increment operator:

In modern Swift you have to write:

As much as I loved to type ++ to increment the value of a variable there was a big problem with x++! Most coders, including me, were using it the wrong way! The correct way for most use cases is:

Most of the time the difference in side effects between ++x and x++ were immaterial, except when it wasn’t and it created hard to track down bugs in code that looked perfectly ok.

So now I’m used to typing += to increment values even in programming languages where ++ is legal. (Also, C++ should rebrand itself as C+=1.)

Another big change for me was giving up for-loops for functional expressions like map, reduce, and filter. As a young man when I wanted to find a particular object in an array of objects I would loop through the array and test for a key I was interested in:

Nothing is wrong with this code—it works. Well, actually there is a lot wrong with it:

  • It’s not very concise
  • I should probably have used a dictionary and not an array
  • What if I accidentally try to change o or objects inside this loop?
  • If objects is a lengthy array it might take some time to get to 12345
  • What if there is more than one o with the id of 12345?
  • This for-loop works but like x++: it can be the source of subtle, hard to kill bugs while looking so innocent.

But I’ve learned a new trick! In Swift I let the filter expression do all this work for me!

In that single line of code o will be the first object that satisfies the test id == 12345. Pretty short and sweet!

At first, I found the functional idiom of Swift to be a little weird looking. By weird I mean it looks a lot like the Perl programming language to me! But I learned to stop being too idiomatic and to allow myself to express functional syntax as needed.

For you JavaScript or C programmers out there here is a cheat sheet to understanding how this functional filtering works:

  • let means o is a constant, not a mutable variable. Functional programing prefers constants because you can’t change them accidentally!
  • The { } represents a closure that contains a function and Swift has special syntactic sugar that allows you to omit a whole bunch of typing if the function in the closure is the last or only parameter of the calling function. (Remember in functional programming functions are first class citizen and can be pass around like variables!)
  • $0 is a shortcut for the first parameter passed to your closure. So you don’t have to bother with throw away names like temp or i,j,k,x, or y.
  • .first! is a neat way to get [0], the first element of an array. The ! means you know it can’t fail to find at least one element. (Don’t use the ! after .first unless you are 100% sure your array contains what you are looking for!)

I’m working on a new project, a game that I hope to share with you soon. The game itself won’t be very interesting. I find that I enjoy creating games more than I enjoy playing them so I’m not going to put too much effort in creating the next Candy Crush or Minecraft. But I will blog about it as I work thought the problems I’ve set for my self.

Notes on NSUserPreferences

You can set and get NSUserPreferences from any view controller and the app delegate to they are a great way to pass data around the various parts of your iOS App.

Note: NSUserPreferences don’t cross the iOS/watchOS boundry. iOS and watchOS apps each have their own set of NSUserPreferences.

In the example below you have a class Bool property that you want to track between user sessions.

In the code above…
– The var showAll is the data model for a switch object value
– The string savedShowAll is the key for the stored value
– Use NSUserDefaults.standardUserDefaults().objectForKey() to access a stored value
– Use the if let idiom as the stored value might not exist
– Use NSUserDefaults.standardUserDefaults().setObject() to save the value
– Apparently setObject() never fails! 😀

On the Naming of Functions

A thoughtful coder once said that “it’s more important to have well organized code than any code at all.” Actually several leading coders have said this. So I’ll append my name to the end of that long linked list.

I’m trying to develop my own system for naming functions such that it’s relatively obvious what those functions do in a general sense. Apple, Google, Microsoft and more all have conventions and rules for naming functions. Apple’s conventions are the ones I know the best. For some reason Apple finds the word “get” unpleasing while “set” is unavoidable. So you’ll never see getTitle() as an Apple function name but you will see setTitle(). This feels a little odd to me as title() could be used to set or get a title but getTitle clearly does one job only. I know that title() without an argument can’t set anything but I’m ok with the “set” all the same.

So far I’m testing out the following function naming conventions:

  • calcNoun(): dynamically calculates a noun based on the current state of internal properties
  • cleanNoun(): returns a junk-free normalized version of a noun
  • clearNoun(): removes any data from a noun and returns it to its original state
  • createNoun(): statically synthesizes a noun from nothing
  • updateNoun(): updates the data that a noun contains based on the current state of internal properties
  • getNoun(): dynamically gets a noun from an external source like a web server

As you can see I like verbs in front of my nouns. In my little world functions are actions while properties are nouns.

calcNoun(), createNoun(), and getNoun() are all means of generating an object and with a semantic signal about the process of generation.

cleanNoun() returns a scrubbed version of an object as a value. This is really best for Strings and Numbers which tend to accumulate whitespace and other gunk from the Internet and user input.

clearNoun() and updateNoun() are both means for populating the data that an object contains that signal the end state of the updating process. (Maybe I should have one update function and pass in “clear” data but many times clearing is substantially different from updating.)

I hope this helps my code stay organized without wasting my time trying to map the purpose of a function to my verb-noun conventions!

Code Markup in Xcode

Screen Shot 2016-05-28 at 12.58.13 PM

I’m working on a fairly large Swift project. Actually no, that’s not quite true. I’m working on a Swift project with a ViewController file that is getting disorganized and out of control. If this keeps up I might have a large project on my hands but right now it’s just a single file that is getting larger than I would like.

Apple provides some quick and dirty tools that make it easy to navigate a single file with specially formatted comments in your code. This functionality doesn’t provide automated documentation like Headerdoc. And that’s fine with me. I like how Headerdoc has become a mash up of Markdown and JavaDoc. My code is just not stable enough for documenting yet.

Happily Xcode’s built-in special comment parser is enough in the early stages of development to help me navigate a large file and remember where the bodies are buried.

Xcode supports the following out of the box:

  • MARK: (your text here)
  • MARK: – (section divider)
  • ???: Question
  • !!!!: Warning
  • TODO: Task
  • FIXME: Bug

Xcode’s special comments mark up the function navigation  pop-up menu so that you can find your questions, warnings, tasks, and bugs in your code without a overtaxing your the private neural network in your skull. Unfortunately you can’t add new special comments and they don’t show up in the Symbol Navigator.

(Using the MARK: comment you can simulate adding your own special comments. MARK: doesn’t add the word MARK: in front of navigation items in the way that the other special comments do (TODO, FIXME, etc.). So you can use MARK: NOTE to navigate to notes in your Swift code if that makes you happy.)

I use the following additional special comments to keep my code organized and consistent. (Xcode will just ignore them unless I prefix each with MARK:)

  • NOTE: (when the function name is not enough)
  • HINT: (a non-obvious reminder about a bit of code)
  • DBUG: (end of line comment marking code that probably should be removed eventually)
  • DEMO: (example usage)

It would be nice if Apple allowed us to personalize code markup in Xcode. But only after search and ranking in the App Store are fixed and a 1000 other higher priories are done!

C Plus Minus

While consuming Handmade Hero and coding furiously to keep up with Casy Muratori I discovered the joy of programming in a language that I deeply understand. This is not one of those new trendy programming languages that tries to be type-safe without explicit types or functional without being confusing. And yet all the new hot/cool programming languages are based on this ur-language. Swift, TypeScript, Go, C++14, and Java 8 are all “c-like” languages and the original “c-like” language is a lingo that we used to call C+- (C Plus Minus).

I probably like C because it was the first non-toy programming language that I used to program a real personal computer. In the late 1980s all the home computers came with BASIC (which is best SHOUTED in CAPS). But once I got a true personal computer, a Macintosh 512Ke, that could run real applications I had to buy a real programming language to write those real applications. For a couple of months that real language was Pascal… but C rapidly took over. By the time I got to Apple in the early 1990s C++ was about to push C out of the way as the hot new programmer’s tool.

We have this same problem today. There is always another more productive, safer, more readable programming language around the corner. If you code on the backend for a living you’re probably thinking about Go or Rust. If you code on the front side you’re ditiching CoffeeScript for TypeScript or just sticking with JavaScript until the next version, ECMA Script 6, shows up in your minimum target browser.

But I’ve been traveling back in time and happily coding away with access to pointers and pointer arithmetic, pound defines, and user designed types. It’s not plain vanilla C because like Cory, I’m compiling my code with a modern C++ compiler. I’m just not using 90% of C++’s features. Back in the 1980/90s we call this language C+-. Back then only some of the C++ standard had been implemented in our compliers. We had classes but not multiple inheritance. (Later we learned that multiple inheritance was bad or at least poor taste so not having access to it was ok.) We only had public and private members. (Protected members aren’t actually useful unless you’re working on a big team or writing a framework. We were writing small apps in small teams.) We had to allocate memory on the heap and dispose of it. So we allocated most of what we needed up front and sub-allocated it. We didn’t have garbage collection, we didn’t even know about garbage collection, so we couldn’t feel bad. We felt powerful.

Now that I’ve been writing in C+- for a few weeks I feel like Superman–Or maybe Batman–Your pick. I have just a few tools in my tool belt but I know how to use them. In the modern world Swift 3.o is thinking of getting rid of the ++ operator and the for(;;){} loop. I use those language features every day, usually together: for(i = 0; i < count; i++) {}. I am told these things are ugly. They seem like familiar old friends to me!

One thing I really like is that I can access a value and increment a pointer with one pretty little expression: *pointer++. I like thinking in bytes and bits and memory addresses. And I like how fast my little programs run and how small their file sizes are.

I know I should not like all these things. Raw access to memory is dangerous. &-ing and |-ing bits is probably dangerous too. My state is not safely closured and side-effects abound. But modern C++ compilers and tools like GCC and Clang do a pretty good job of catching memory access errors these days. It was much more dangerous back in 1986 back when I first started.

Maybe I’m just nostalgic. But while you are learning Swift or TypeScript to write web and mobile apps the operating system your computer runs (Mac OS X, Windows, Linux) was written in C+-. The web browser (Safari, Firefox, or Chrome) that renders your HTML, CSS, and JS was written in C+-. That awesome AAA game and Node.JS were written in C+-. (Some parts C, some parts C++ and some parts Assembly as needed.)

C+- is the Fight Club of computer languages: Nobody talks about it, it doesn’t have official status, and groups of self organizing coders beat each other up with it every day.

Binge Watching Handmade Hero

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For the last several weeks I’ve been obsessed with one TV show. It’s changed my viewing habits, my buying habits, and my computing habits. Technically it’s not even a “TV show” (if your definition of that term doesn’t include content created by non-professionals that is only available for free over the Internet).

But for me, a more or less typical Gen-Xer, Handmade Hero by game tool developer Casey Muratori has me totally enthralled as only must see TV can enthrall. I’m hooked and I simply must watch all 256+ episodes of Handmade Hero before I die (in about 1,406 Saturdays according to the How Many Saturdays app).

So first off let me explain a few things. Unless you are an aspiring retro game programmer or aging C/C++ programmer Handmade Hero will seem tedious at best and irrelevant at worst. There are much better and more modern ways to make a video game (like SpriteKit on iOS or Unity on any OS) but Casey promises to demonstrate live on Twitch.TV how to write a complete video game from scratch, without modern frameworks, that will run on almost anything with a CPU. He’s starting with Windows but promises Mac OS X, Linux, and Raspberry Pi.

This is a bold promise! When I first heard of Handmade hero, almost 2 years ago I ignored it. I didn’t know who Casey Muratori was and the Internet is littered with hundreds of these solo projects that tend to fissile out like ignobly failed Kickstarter projects.

But a comment in Hacker News caught my eye about a month ago. Casey had delivered hundreds of hours of live coding with explanations of arcane C, Windows, and video programming techniques! It’s all archived on YouTube and he’s still steaming almost every night! Awesomesause!

So I had to check it out. I started with Casey’s first video, Intro to C on Windows, and ate it up. I had to pound through the rest of that week’s archive. Because I have a family and a very demand job and kids and cats I had to purchase a subscription to YouTube Red so that I could watch Casey’s videos on or offline. Google is getting $10 bucks a month off me of because of Casey!

My keyboarding fingers ached to follow along coding as Casey coded. I used to be a C/C++ programmer. I used to do pointer arithmetic and #DEFINEs and even Win32 development! Could I too write a video game from scratch with no frameworks? I had to buy a Windows laptop and find out! Thus Dell got me to buy a refurbished XPS 13 because of Casey!

Even Microsoft benefited. I subscribed to Office 365 for OneDrive so I could easily backup my files and use the Office apps since I’m keeping my MacBook Pro at the office these days. I have discovered that a Windows PC does almost everything a MacBook does because of Casey!

I usually have less than an hour a day to watch TV so I’ve had to optimize my entertainment and computing environment around Handmade hero because at this rate I will never catch up to the live stream! But I’m having a blast and learning deep insights from a journeyman coder.

What could an old school game coder teach an old battle-scared industry vet like me? More than I could have imagined.

First of call Casey is an opinionated software developer with a narrow focus and an idiosyncratic coding style. He is not wasting his time following the endless trends of modern coding. He is not worried about which new JavaScript dialect he is going master this month or which new isometric web framework he is going wrestle with. He codes in C with some C++ extensions, he uses Emacs as his editor, he builds with batch files, and debugs with VisualStudio. While these tools have changed over the years Casey has not. He is nothing if not focused.

Thus Casey is a master of extemporaneous coding while explaining–the kind that every software engineer fears during Google and Facebook interviews. This means Casey has his coding skills down cold. He is unflappable.

Casey doesn’t know everything and his technique for searching MSDN while writing code shows how fancy IDEs with auto-completion are actually bad for us developers. He uses the Internet (and Google search) not as a crutch to copy and paste code but as a tool to dig deep into how APIs and compilers actually work. There seems to be nothing Casey can’t code himself.

Casey makes mistakes and correct himself. He writes // Notes and // TODOs in his code to follow up with as if he is working with team. Casey interacts with his audience at the end of every stream and is not shy about either dismissing their questions or embracing them. Casey is becoming a better, more knowledgeable programming before our eyes and we’re helping him while he is helping us.

Casey is not cool or suave on camera. He swigs almond milk and walks away off screen to get stuff during the stream. But nothing about Handmade Hero would be substantially improved if Casey hired a professional video production team. In point of fact, any move away from his amateur production values would be met with suspicion from his audience. Any inorganic product placement would fail. Dell, Microsoft, and Google should support him but stay the heck away least they burst the bubble of pure peer-to-peer show-and-tell that surrounds Casey.

I have 249 videos go to (and Casey has not stopped making videos)! I still don’t know if he delivers on his promise and creates an actual video game from scratch. (Please! No spoilers!) But I already know far more than I did about real-world game development where the gritty reality of incompatible file systems and operating platform nuances make Object Oriented Programming and interpreted bytecode luxuries a working developer can’t afford.


In Defense of Bubble Sort

Bubble sort is an algorithm with a very bad reputation. Robert Sedgwick, in Algorithms in C, notes that bubble sort is “an elementary sorting method” and “it does much more work” than it needs to. Donald Knuth is much more harsh when he states “the bubble sort seems to have nothing to recommend it, except a catchy name…” in the Art of Computer Programming.

Like a an actor valued only for his good looks bubble sort is an algorithm an enterprising coder should probably not admire.

Why is bubble sort so bad? Why does decent computer society advise young and impressionable software engineers avoid it? Why am I devoting a whole blog post to the ugliest sorting algorithms?

TIL: You can learn more from the flawed than you can from the flawless.

I’m not going to tell you why bubble sort is so bad. But before you google it why not try to figure out on your own?

The truth is that modern programmers don’t usually implement any standard sorting routines on the job—even the good ones! Generally there exists a collection class or library that is well written and well tested. If you have a mentor she will tell you not to bother with your own interpretations of the standard body of algorithms. That problem as been solved.

However, I think you’re missing out. Knowing now to implement well known algorithms can help you understand when to use them, what their strengths and weaknesses are, and how to talk about them. Like in a job interview.

Bubble sort is a great place to start. In order to understand why it’s so bad you have to understand big O notation, how algorithms are classified, and how the ordering of input data impacts the performance of an algorithm.

It’s my opinion that bubble sort is only the most terribad sorting method in the platonic world of absolute randomly unordered data. Bubble sort is actually very appropriate for error detection or for data that is already mostly sorted. You know, the kind of data that you are likely to run into in real life.

Identity used to sign executable no longer valid

The last thing I wanted to do on a Sunday morning is write a blog post about an an Xcode executable problem. What I had planned to do is test my most recent Swift 2.0 SpriteKit game on my iPad and iPhone. Last night I got a “Identity used to sign the executable is no longer valid” error when attempting to run my code on a real device. Since it was around midnight I took the message a notification that bedtime had arrived. Besides, a quick search on StackOverflow would surely solve the problem and if I got on SO now I would be up all night nosing around.

This morning I got the same message and found a post on SO that started  four years ago with two pages of answers: The identity used to sign the executable is no longer valid. It’s been viewed 66K times and covers many ancient versions of Xcode. The top answer simply said to restart Xcode. Indeed, restarting, rebooting, or re-installing is always a great answer! So I tried the first two (restarting Xcode and rebooting all my devices) but no joy. And it’s a cheap answer. 99% of computer problems are temporarily solved by powering down and up the server or device but the root cause sits like a malignant elf in the machine, biding it’s time, ready to strike again.

So I figured it out. My problem, in any case.

Last week I was giving a talk at SUNY Buffalo (shout out to Prof. Hartloff). It’s just far enough away from NYC that I had to stay overnight. I took a MacBook Pro that I don’t ordinarily use for development. When I was working on my new game and testing it my iPad and iPhone (to get actual frame rates and the feel of touching the screen) Xcode discovered that I didn’t have an iOS development certificate on that MacBook and asked me if I wanted to revoke my current cert or copy it over from another machine. Since I didn’t have it I said revoke. Xcode did what ever it does and created me a new iOS dev cert associated with that particular MacBook Pro.

Note to Apple: There has to be a better way for Apple certified developers to manage their certificates in this age of clouds and connectivity. Can’t these certs reside on Infinite Loop server?

Enough backstory!

If you get the dreaded “Identity used to sign executable no longer valid” error and restarting your Xcode doesn’t work here are the steps that should fix it for good.

Go to your Apple developer account certificate overview and read carefully and completely about how to manually manage certs and provision devices. Once you understand what you need to do it’s relatively simple.

  1. Revoke and delete all the could certs and profiles of devices you no longer own that have build up over the years. Clean it all up.
  2. Then, following the instructions from Apple recreate your iOS development and distribution certificates.
  3. Re-provision your iOS devices.
  4. Download your certs and provisioning files and reinstall them into your Mac’s keychain.
  5. Clean and build your app.
  6. Now it should run on the iOS devices you’ve provisioned nicely.

Note to You: Xcode is no longer managing your certs and profiles. But that’s OK. It was doing a bad job anyway.

Post Script

Why didn’t I post this info to Stack Overflow? Because this is a pretty radical solution, not without risk. SO, for better or worse, has been come the place for copy and paste solutions that have not aged gracefully over time. Don’t get me wrong–I love Stack Overflow, recommend it, and use it all the time. But sometimes it’s not safe to post an answer to a problem that requires reading comprehension.

Lucky for you and me, my unpopular blog post will probably be the last item in your search for solutions to apple certification problems.