Command Pattern in Unity

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The Command Pattern is one of many design patterns that every game dev and programmer should have in their developer toolbox. In this video I'll use a practical example to show you how to implement the Command Pattern in Unity, and explain what the Command Pattern is and when it's useful.
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00:00 Introduction
00:40 Sign up for the Level_2 Game Dev Newsletter
01:08 Example Project Overview
02:24 Undo Feature Implementation
08:18 Command Pattern Explained
09:43 Conclusion
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[@InfallibleCode]

🚀 Sign up for the Level 2 Game Dev Newsletter: eepurl.com/gGb8eP 📦 Download the project files (Tier 2 Patrons): www.patreon.com/posts/62244189

[@ukl2901]

Most unity tutorials start from basics and end at basics but I have found your channel to be the only one which gives good information for low to mid level devs who want to jump their careers. Its amazing what you are doing and hope you continue doing it

[@InfallibleCode]

I really appreciate that feedback 🙏 My only goal is to provide valuable to this awesome community of game devs :D

[@wlsmdltn]

Me too same thinking as you. Deep thank to youtuber!

[@iHeartGameDev]

Awesome video, Charles! Funny enough, I’m working on this exact pattern at the moment too 🎉 Your explanation’s level of quality here has certainly raised the bar! This was incredibly well done 👏

[@saito853]

This was what I did for an RTS prototype that I never finished. This pattern allows you to create a system that controls a mass number of unit of different types very easily.

[@AnikenSkiwalker]

Charles, you are a Jedi of Coders. The strength of your teaching is your ability and emphasis is actually implementation of these concepts. Thank you. THE CODE IS WITH YOU.

[@stefanandersson7519]

I think a nice addition to your videos could be to make like a visual overview of the different components of a pattern, how they relate to each other, and what class they correspond to in your example project - like a mind-map, you know? I have a really hard time keeping multiple things in my head at once, but if I just have one image to look over and study it becomes a lot easier to grasp. Still a great video, I love learning about new patterns, makes me feel so much more professional :)

[@InfallibleCode]

Great point, thank you for the suggestion! I'll try to work more visualizations into my future videos so that the concepts are a little clearer to visual learners.

[@cheeseriners]

I was just going to comment this. I got a bit lost during the video, I understood the idea behind, but the implementation was a little fuzzy for me.

[@programming1784]

@@InfallibleCode UML diagrams. Also, why do you use an abstract base class? I recall from the GoF or Head First implementation that there is an interface ICommand for commands indtead of an abstract class. Curious to hear why you chose this approach?

[@andrewdudas3288]

This video was incredibly well timed, I had just decided to try and implement a replay feature into my project and then this video went up on the exact same day. I just finished implementing this into my game and I am watching the game replay itself on my other screen. It is extremely satisfying to watch. Thank you.

[@LaCreArthur]

I love how chill and cosy the setup is in the few last videos! Keep it up Charles, awesome work!

[@MrHandsy]

I am using the command pattern and scriptableobjects to create abilities in my game. The pattern is amazingly useful.

[@ledjfou125]

You are simply amazing, I spent my morning binging your channel and learning a shit ton ! You are a great great intermediate advanced teaching ressources ! Seriously so much better than most of the basic unity videos out there that don't do clean code most of the time ! Thank you like so freaking much !

[@InfallibleCode]

I really appreciate your feedback and I'm glad to hear that you're finding my content helpful :D

[@09mrbubbles]

Your topics are just pushing the boundaries of my knowledge. I appreciate you levelling me up!!

[@InfallibleCode]

That's exactly where you want to be! Keep on pushing those limits :D

[@gamedev1905]

When I first started my career 10 years ago, I had to abandon my first big project because, at the time, I didn't really understand functional programming and without it, my codebase ballooned in size and complexity. This is a very good design pattern that solves the problem that I ran into back then: my turns needed to execute their actions in an MTG style stack, and this is how you do that.

[@ankitr1999]

The quality of your tutorials is amazing!

[@InfallibleCode]

Thank you!

[@voizeh7140]

Thanks for tutorial! And I think it's bad, that you call Execute( ) in Record( ) method. Because Record( ) should only record, not call

[@wrewrrwe]

I think that's a good point. I also thought about it.

[@reishin6]

I was thinking the same thing. Recorder class should not be responsible for executing the action, it should only be recording it.

[@jonahmcconnell4818]

Great tutorial as always!

[@andrewtse3401]

Great Video! Does the Editor Console Pro 2 Link in descriptions also lead to Rainbow Folders 2? Can't seem to navigate to it.

[@devinweidinger3812]

My spider senses were tingling and brought me to this video :D Thank you for covering these great design patterns! Great resource for devs!

[@InfallibleCode]

Haha nice! I'm glad you're finding these design pattern videos useful. I definitely want to do more :)

[@huuphunguyen9136]

exactly good stuff that I have expected

[@nexxogen]

What I don't like about this is the fact that the recorder is running the actions too. If I was new to this project and looked at the input callbacks, I would only see method names called "record" and it wouldn't be clear to me that those are also running the actions and not only recording them. Also, when something is called a "recorder", I think that you're breaking the "one job per class" principle when you also make it do other things besides recording. I would try to keep running the actions and recording the actions decoupled.

[@BBdaCosta]

Awesome video, I Would love to watch this implementation usinf TDD methodology. I think that people need more examples of implementing tests in Unity.

[@InfallibleCode]

Totally agree!

[@XxMeuktwoxX]

Hi Charles - thank you for the great video! Quick question - what do you think about including things like UML diagrams to your videos, to help visualise how these all link together?

[@InfallibleCode]

Thanks for the suggestion-I think it's a great idea! I've done UML diagrams in the past and am happy to include them in future videos :)

[@adamcervenec6897]

This is just another level tutorials compared to others. Perfect !

[@InfallibleCode]

Much appreciated!

[@D-Dev]

Another good video, but I have a question unrelateed to this video topic. How you create this background in this level, because I don't know how to create this disappear in fog effect which we can see on right site of the board object.

[@cobaltblue73]

Just wanted to add that this pattern is a core pattern in writing solid net code with any sort of rollback implementation. All the tutorials on youtube about online-multiplayer games in Unity talk about RPCs, packets, protocols... etc. But they never bring up this pattern. I would even go so far to say any singlple player game which was written on a good implementation of the command pattern is that much easier to convert to an online multiplayer game...

[@cobaltblue73]

@NiceLife Lol that's a tall order to ask for in a YT comment. Ok here goes... So I'm gonna use PUN terminology for context (full disclosure I haven't used PUN for a while now so if I get some terms wrong please spare me). So PUN and a lot of other multiplayer libraries have RPCs right... so with RPCs your client receives the RPC call and changes some sort of game state, sometimes the changes are straight forwad and simple but sometimes it changes a lot of variables or sometimes it's a small change that starts a crazy chain reaction... Sure you can try to brute force it and sync all the game changes in game state but there's an upper limit to that. Most modern action games rely on the assumption the game simulation is determinisic such that given input X you will get output Y. So in a snappy action game the clients are running as much of the game locally in parallel and double checking if everything is synced after the fact. But nothing is perfect. A client might loose packets, one of the clients might bug out that causes a butterfly effect that causes the game state to desync overtime. So when that happens if your RPCs were just taking in some data and just applying those changes immediately, those changes are "ephemeral" and are lost by the next RPC call. However if your RPCs were converting the received data into commands then keeping a record of those commands if any any desyncing happens then a client could go ask the host client or the server to compare their command record to see if there are any discrepancies. Then after getting the lost command they could re-insert the missing commands, undo all the changes of the previous commands all the way to the lost commands then re-apply them. Hopefully if your game simulation is determnistic enough this is the most effective way of re-syncing game states across clients. And this is what's commonly called rollback net code. Phew... ok enjoy this wall of text....

[@cobaltblue73]

@NiceLife Disclaimer this is still an over simplification and highly dependent on the type of game that you're making. Well I'm glad it helped...

[@Void-vn2vf]

Great video, as always :)

[@InfallibleCode]

Thank you!

[@SaiponathGames]

Really cool video, it was pretty helpful to be honest.

[@InfallibleCode]

Glad to hear it!

[@birgerevan]

Hey Charles! I've been trying to learn DOTS for a while now. Although i love the mindset of working with data I've been having trouble actually making something more than a test project (rendering in 2d, animations, camera, sound etc). I'd really appreciate a tutorial on practically using dots for a game!

[@work3644]

Cool tutorial! Please make a character controller system with an advanced state machine - I think it will be great! :)

[@Fred-ju1xs]

I'm new to abstract methods. I noticed JumpAction's execution method used _unit.Move(_direction) //this wasn't changed even after the abstract class was made But in the abstract class, the execution method used Unit.Move(_direction) When you use abstract classes you don't have to use the defined _unit variable anymore?

[@suchasaltylemon9850]

I'm a simple man: I see infallible code, I click

[@InfallibleCode]

And I thank you for that :D

[@Arturrabbit]

love your content

[@LukeCloudrunner]

Great video Charles! Is there a reason to use a base class over an interface for the ActionBase script? To me it seems both are suitable

[@InfallibleCode]

Just a force of habit. In Unity, I usually start out with an abstract class that derives from MonoBehaviour and push the abstraction down to an interface only if I need to test something or facilitate a more sophisticated API.

[@pudgystump]

Very nice!

[@evggg]

I didn't understand how spin works and what jump does. Is a jump just a jump in spot (no horizontal movement)? If we spin clockwise, then in the undo method we must spin counterclockwise.

[@artillepsy3172]

Perfect quality content

[@InfallibleCode]

Wow, thank you!

[@namtranhai8456]

I am developing a house-building game. This have some mode that allow you to do plenty of task what share similar input. In these case do I have to create a command and an invoker base for each mode.

[@themediocre_coder]

How did you do that at 5:48 ???

[@V-post]

What IDE are you using? I like it much better than VS

[@jorgevandesompel8676]

I subscribed to your newsletter, but I can't find the lifecycle hook where I need to unsubscribe. I'm really afraid of a memory leak. Could you help me find it?

[@InfallibleCode]

The unsubscribe event was a little buggy so we removed it from the code ;P

[@disturb16]

Great content

[@lor1024]

Any one knows what the font family is in the video? I looks comfortable for coding!

[@masoetic4668]

That great dude!👌👌👌

[@InfallibleCode]

Thank you!

[@Xedroid]

Great video! What do you think about using this pattern for a player skill system where each skill use is action / command. I wonder if this can be inefficient on systems where a large number of actions / commands are triggered in a short time because each action is a new instance of an object?

[@InfallibleCode]

I think the Command pattern could definitely provide a good approach to a skill system. And if performance became an issue, you could use a factory pattern to either create new actions or grab existing ones that weren't being used from an object pool.

[@Xedroid]

@@InfallibleCode thanks

[@Cextra_the_artist]

Page redirection after subscribing to the newsletter appears to be broken

[@MaksMikhnevych]

You can make the Recorder class public static, no need for monobehaviour here and extra editor reference.

[@otrocanalmas8096]

Man , this video is Great. Can you tellme please wich Code editor are you using ? Thanks

[@Masticater]

He's using Rider

[@otrocanalmas8096]

@@Masticater Rider ? Ok thank you , i shall check it ... could you tell me please what are the Pros - vs Visual Studio ? :)

[@Masticater]

@@otrocanalmas8096 VS is free

[@fast07hzmc401]

Really nice video (:

[@InfallibleCode]

Appreciate it :)

[@otrocanalmas8096]

Dude , i have another question . This actions can be recorded using interfaces instead SuperClases ?

[@InfallibleCode]

Great minds think alike! Thank you for the accolades, Nicky 🙏

[@dominiquekostler238]

Would be interesting if you also showed the redo functionality since this is lost once the action is popped off the stack.

[@MarekNijaki]

You could also talk little bit about garbage collection associated with this pattern and how you can mitigate it. Overall great video

[@Adoblem]

great video

[@InfallibleCode]

Glad you enjoyed it

[@iiMintyHippo]

I got lost at the action recorder part of the code, to me it seems so impossible to learn how to understand that but I will keep trying.

[@InfallibleCode]

Don’t give up!

[@rolepg8149]

How we can reduce the size of rewindable actions in a larger entity count ? and thanks :)

[@InfallibleCode]

There are a few things you can do. For one, you could use object pooling to limit the number of commands that are created. Another thing you could do it use anonymous functions, also known as lambdas or closures, to represent commands instead of Objects.

[@aguscm23]

Which IDE are you using in the video?

[@Shorkiedokey]

Rider

[@aguscm23]

@@Shorkiedokey Thank you!

[@Renusek]

Why AcrionRecorder class is MonoBehaviour? It doesn't need to be from what I see.

[@bogoid]

Jebtrains user? Instant subscribe

[@In-N-Out333]

How did he write that equal sign with a slash through it?

[@InfallibleCode]

It's a special character called a "ligature". The font that I use (and many others that you can download) include ligatures that show up in your code editor if you have them enabled. For reference, the font I use is called Victor Mono: rubjo.github.io/victor-mono

[@homeofgamesnews]

Nice video, i making a game where you can control the player by using visual coding such as Bolt, and i used the command design pattern to implement the visual coding system in the game, and that gives me a massive flexibility during game programming.

[@InfallibleCode]

That's a really neat use case, thanks for sharing!

[@bobaman8957]

Can you do a video about floating point error No one in youtube explain that 😢😢

[@nilmag2284]

you're better than "var" man, we all are!

[@WaveEchos]

Oh... thought that you would doing command inputs for like fireball/dp motions and stuff. Though what is here is pretty close to what is needed for one. Edit: Including netcode rollback

[@Guil118]

Dude! How did you manage to display a "!=" as a single symbol?

[@mohokhachai]

Wait command

[@DaydreamStudios_Official]

Why Does No One Ever Use #regions They Just Make Life Better

[@monkeyrobotsinc.9875]

this must be another advanced tutorial, because im intermediate and i cant follow this. damn!!!!!!

[@w0nnafight]

Did you start taking schizophrenia pills?