It took me a frustratingly long time to grasp state machines, but your first video on those helped me immensly. Having worked with them now for a while by now, this comes at the perfect time to think and tool with it a bit more :D!

Some points I'd make on State Machine design, since I'm quite passionate about those: - Avoid the term "Manager" unless the system is intended to be used once in a game scene. FSMs are very frequently used in character behaviour systems to control decisions, actions, animations, sounds and so on. Those are per-entity usages. Why not just call a spade a spade. It's the state machine that handles the states, regadless of whether it's one instance or a 100 instances in a scene. No better name than just "StateMachine" imo. - Use Message Passing. Anytime the current state or an external system wants to trigger a next state, store it in the SM in a private field instead of having the SM specifically asking the current state "hey do you have a next state for me?". Use a "private EState queuedState;" field instead. - There's high value in talking about the differences between a SM that internally decides when to switch states, or one that expects external systems to switch. Is there deliberate intention behind the transition method being public? This allows state transitions as a direct call from external systems, instead of handling that in the SMs own Update (see the previous point). - The dictionary approach severly restricts how State instances must be made. For one, they must be registered for every FSM when the FSM is initialized. Secondly, that also means they must be pre-defined which prevents dynamic adjustments to the state members. Thirdly, it expects a one-to-one mapping. This means a Walk vs Run state needs two separate enum values despite all the code behaviour being the exact same, only with the speed being the difference. Now imagine having a "slowedWalk", "boostedRun", "Sprint" and other variations. All of those could instead just be done during state construction, i.e.: "stateMachine.QueueNextState(new MoveState(moveSpeed))" where the moveSpeed could stay very dynamic throughout the game. There are other ways of passing movement speed but I think it serves as an example of flexible design. - Show an implementation of the initialization of these classes, in practical examples. How is the dictionary populated, how is the first state going to be set. Should the SM assume that there is such a thing as a "default" state. Should the SM allow having no state at all in some cases? - Flexibility in decision making. If a state needs to tell the SM what the next state is, it means that this state will act the same in most cases. Of course there can be some logic as to what state should be picked, but imagine using state for the character behaviour in an action game. If a state is to move to a location, how does the movement know what comes next? Should the character swing a sword or try open a door? A move state wouldn't know the answer without a lot of complexity that doesn't concern how movement is done (which contradicts SOLID principles). So if the movement completes, how should the next state be chosen. This ties into the use of a "default state" but also the thought about "external state decisions". This is also the biggest difference between a mere FSM and a fully fledged BehaviourTree. Although I would recommend a combination of the two.

✨Very excited to share a new tutorial with you all! What is your favorite design pattern? It's pretty clear what mine is... 😂

It is very uncommon for GameDev videos to get as deep and accurate in the OOP concepts and patterns. Most Game Dev videos focus on "make it work", you focused on "make it ELEGANT". Plus, the implementation is perfectly balanced between simplicity and reusability. Great work !

One tip. At 8:44 you can use a guard clause for IsTransitioningState. It will increase your code readability.

Even tho I knew these things already I still watched the whole thing cause it's so well edited and well explained, appreciate your work a lot man keep it up!

8:40 Update is called on the mainthread, there is no parallelization happening. As long as no ExitState or EnterState method calls "TransitionToState" there is no need for "IsTransitioningState". Update is also only called Once per frame. Also, I find the design questioning that your state decides the following state. The state should not depend on other states at all, keeping it modular and interchangeable. the transitions should be defined on the state machine (or state manager) - imho. There might be applications for changing this, but I'm referring to a general purpose state machine

It's always nice to see more about fsms. Something I would like to see in event-based transitions!

I loved your older tutorial about state machines. Right now, your type of implementation is what I commonly use, with some tweaks! I just opened UKposts because I want to see other state machine's implementations and KABOOM! You are here. Amazing, as always a very nice video. Keep on!

Incredibly useful and well explained, as always

After about a week of frustration trying to wrap my head around it, I've finally managed to use this and your last couple of state machine videos to create a reuseable heirarchical state machine 🎉 Now to implement it as a character controller using event based state changes 😅 Thanks for the fantastic tutorials!

Hey man I really really like your videos. I have struggled quite a lot with state machines, yet i`m still struggling with some stuff but you are making it really easy for everyone to understand. I generally got a good idea how do state machine works, yet I still lack some understanding how to implement movement controls (as for fps character). So, I would like to ask you, if possible, maybe in a future video to show us an example of FSM of a FPS controller (based on a rigid body movement) and the new unity input system (which is based on input events). I assume since it's really hard for me to grasp all the aspects of it, that there are lot of people having the same troubles. Thank you for all the good tutorials so far!!!

Thank you, this was really helpful! Just in time for my next game jam. I had been looking for a way to refactor my overly complicated state machine mess, and this was it! It integrates perfectly with my current system

Awesome, thanks for the series.

It's also useful to have a method to reset the state when the transition is happening (although that can just be inserted into the Exit method, I just find it cleaner to have a separate method for it). That is for when states are reused and not recreated (for example to avoid garbage allocation - it's a microoptimization for performance since on devices like mobile, a run of the garbage collector can actually cause some microstuttering - also tied into that: Dictionaries with enum keys will generate garbage as well. A workaround would be to a dictionary that maps from int to the state. This is a bit less type safe though). Another interesting implementation I've seen is to not deal with Enums, but with the "Type" type directly as dictionary key type. Then there are possibly some other design decisions people can make for themselves: Should the state machine manager check for a changed state itself, like here, or should each state trigger the Transition method directly. Is it allowed to transition from a type of state to the same type, or not? (most often, it is probably not necessary) What might also be useful is some sort of shared data container to store state in, so that states can cross access this. Such a container could be created by the state machine, or passed into the state machine, and then passed on to each state (for example through the state constructor).

This was very informative and well explained! 🙏🏻

Thank you for making this! I'll share it with my students! 📚

Your uploads are always extremely helpful! I wonder if we could get a video on Behavior Trees some day! 😃

Thank you for a great explanation!

Finallyyy 😭😭💖💖💖 thank you so much, I can't wait to get my hands on this code!!

Ur Explanation Is Very Clear Please Dont Stop Doing it ❤

*furious note taking*

Thank you so much for sharing this with us. As a hobbyist gamedev I admit this is still beyond my complete comprehension but I am much closer to fully understanding it. Your video was very well put together and I'm sure I'll be referencing it in the future.

I am confused as to where the logic for these states go. I made a few classes inheriting from BaseState e.g "public class IdleState : BaseState"... I haven't been able to figure out how to use the enum to get this state though. I wonder if maybe I have completely misunderstood the idea here.

I happen to be learning about state machine lately and this tutorial shows up right on time xD

worked! thank you a lot

It might be useful to include variants of this implementation such as utilising a stack in your FSM brain to return to a base state after completion. This would help for menus, states like attack follow-up/combinations and may not be immediately obvious for a fresh game developer.

I admire your perseverance. You are obviously very passionate about some coding patterns (like State Machines lol) and you try to teach them to the Unity community, which is dominated by beginner level coders trying to "make a game" and quitting after it gets serious. Even though the reception of such more intermediate level lessons is not as good as of the standard "flashy FPS game unity tutorial" you don't let yourself get drifted towards the easy market. And for that I wanted to say thanks!

Any plans on potentially expand on this and explain how to incorporate support for substates? And as many others have pointed out, event-based statechanges and such would be very appreciated! That said, fantastic video. I'm trying to learn more about FSM's so this was great. :)

And there he is with another great video.

Excellent intermediate coding video 🎉

Awesome tutorial as always, learned about state machines in your previous videos on the topic! :) However I would appreciate a few minutes of how to use it, create concrete states, add them to dictionary - actual usage. I find it a bit confusing to get started with this! Anyhow, great video, awesome editing etc! Keep up the good work ,you rock!!

Very nice pattern! Thank you so much for sharing. My two cents about it: making the methods of BaseState 'virtual' instead of abstract would allow not to implement them if not needed, leading to less clutter in the implemented states.

Great video! I'm new to state machine patterns. Could you give some examples where actual logic code is implemented in some specific use case? Would logic code be implemented in other new classes, which derrive from Statemamager, or else?

Great video! However, I don't quite understand why we need to check for IsTransitioningState. Following this implementation, Update() is a synchronous method and therefore all of the code (of this and every other Update() method) is executed before the next Update() is invoked. Therefore, there cannot be multiple state transitions at the same time. Even with event-based state transitions, I don't see why we need to check this, as the events should be handled in sequence and not in parallel. Am I wrong?

Thanks for the project. Do you see any difference between using an abstract or a custom class (non-Monobehaviour) with override methods for each state?

Moving to Godot but as great part of your explanations are engine agnostic or can be tried out without much hassle I'll keep following you, thanks for this superb video!

I love this tutorial

Great video. Very informative and well presented. I think there are some improvements that you could make. In the Update, you should short circuit if "isTransitioningState" is true before you call "GetNextState()" so that it doesn't get called every frame. IMO, it's more readable as well. You can see at a glance which conditions will cause subsequent logic to skip. When building abstract classes I think it's important to be as performant as possible. Instead of an update that constantly checks whether the state changes, it would be better to implement an event driven solution. That's probably outside of the scope for this video, though. Overall, great tutorial!

Wait, at 8:20, how could Update() be called multiple times before going through all instructions if the code is executing on the main thread?

Nice design!

How do manage a character, that can have multiple states at once? For example: You attack, while jumping or you block, while walking.

I think you could return a BaseState directly instead of using generics and the enum. So basically the GetNextState returns the new target state.

Great video! I've seen some comments suggesting that statemachine should control when states change, i would say it highly depends on use cases. If you have need for more dynamic statemachine like a hybrid of behaviour tree than yes, this is trouble, but i can see a lot of use cases when this implementation will save statemachine to be bloated and delegate functionality to states themselves. Cool stuff!

Great video ! inherited from MonoBehaviour is not a good idea in my opinion. It would work in more cases / be more flexible if it were just an object usable by composition. But the genericity with the enum is really cool, I didn't have it in my version.

wow never seen this method before!

The modification of this that I made was a bit minor, but instead of using !IsTransitioning as an extra condition in the if statements, I just moved the logic to a different function (StateLoop) with a guarding if statement for IsTransitioning that returns from the function back into update, just so I don't have to repeat the check in both if statements (less of a performance thing and more a readability thing )

Thank you for sharing a very well edited video of your state machine implementation! I was wondering what your reason is to include the OnTriggerEnter/Exit/Stay methods in the base class and making those abstract? I see the point of having non monobehaviour base states and making the OnTrigger functionality available to the states could be beneficial, but wouldn't making those virtual instead reduce some bloating code for child classes that don't require them? Anyway great stuff!

Great job man

what is your suggestion is it better to code for your state machine or use the default animation/animator unity system? cons pros

Hey, I remember recommending using the dictionary to cache your states way back then. Now here you are, teaching me a new and clean way to reuse state machines! I love how that works. I am curious, why are you handling state swapping the way you are? From what I can see, you're taking the indirect approach of having the states return their own keys when asked for the next state key in GetNextState. Wouldn't it be easier to put the responsibility on the states themselves to call the TransitionToState(State stateKey)? As I'm typing this, I realize that by having the states return the next state with a method call, you don't have to cache the state manager! Thats clever, very clever. I find myself bogged down not only by repeatedly making state machines, I always have extra code for keeping that reference in the states. You've taught me two things today!

How exactly do we modify the PlayerState.Idle's methods etc after 9:04 ? Where can I implement my pre-existing methods, I'm confused... :( I am trying to refactor my old CharacterController like you did in your tutorials with this new system but I can't seem to understand. Thanks for the video though!

I was just following your tutorial for a Hierarchical State Machine. I'm building a 2d hack and slash game, and I am mixing my movement and combat mechanics in this state machine. As a result I have 4 super states and A LOT of sub states, with their own nested states. I wanted to ask, do I have to create a script for every substates, that includes their own logic (stun, double jump, special attack, dodge etc)?

Hi I've seen your first tutorial on state machine, and you were passing the StateManager as argument into EnterState(), UpdateState(), and ExitState() so that there's a way to access the player's data. You didn't mention how to pass data from state manager to states in this video - will you suggest the same method here?

your explanation is fantastic everyone can understand it well. I know you teach only the animation system but is there any chance to teach other stuff like Network VFX etc ... ?

Another great video. Please show how to create a 3rd person character controller using this better state machine and the new input system. Thank you!

Thanks for your video! However,I have some problem when using the state machine：I would like to use IEnumerator to make a timer，but in the state class it does not have the StartCoroutine method. should I do the timer in the FixedUpdate method or change the design of state machine？

Hello, can you show me the constructor method of an example state class?

I have a really hard time understanding this right now. How is this reusable? Lets say I have an Agent, that can have multiple states, like Idle, Running, Turning, etc. I would need to write specific states for that agent. So this results in having tons of extra classes at least one for each state. Every State class needs to hold an instance to my Agent class (and potentially other instances with data), so it can for example move my Agent . So the state classes become tightly coupled to my Agent instance or am I missing something? Still cool Video, it popped right up, when I'm coding an AI for my game idea and need to research that topic.

That's excelent~

Would be nice to have an optional exit time that switches a state. Also a fixed follow-up state would be nice to chain states (from shoot to reload to idle). I.e. when magazine is empty, reload occurs which takes a fixed amount of time (read from animation length?) and switches to idle after reload is done. So you can define a fixed "next state" after the reload state has finished. Also a hierarchy would be nice to keep it organized :) And maybe you introduce a "state changed" event other objects can subscribe to, so they can act accordingly (i.e. a camera system that switches states depending on the player state. Switching between shoulder and normal cam when aiming state is active).

LOL I was just talking about State Machines and your videos with my colleagues 20 minutes ago.

Great, very thank u

I want to know without deriving from BaseState how you access it using "CurrentState in StateManager", how does this work & any resources where I can get more info

Thanks for video but I can't understand one think. How can I handle transition between states ? Can you give me an example ? Thank you!

What coding pattern we should use for making games that involves at lot of movements?

Oh heck yes!

Something I would like to see discussed is when to split certain behaviors between multiple state machines vs creating an often complicated hierarchy within a single state machine. I would always get tripped up by whether to keep a player’s traversal state (walk, run, idle) separate from a combat state (attacking, guarding etc.). In summary: when should an SM be split into multiple SMs even if the behaviors interact with each other? (Ex: can only perform certain attack when in x state etc)

I'm sort of new to state machines. I actually watched your first video on state machines just a few days before finding this one. Great work. However, I'm a tad confused about the Update method in the StateManager class. The first line in the method sets nextStateKey = to CurrentState.GetNextState(), but the if statement right after depends on nextStateKey being equal to whatever CurrentState.StateKey is. Unless I'm misunderstanding the purpose of the GetNextState method, I don't see how nextStateKey could ever be equal to CurrentState.StateKey when it's constantly being set to something else one line prior. Need some help understanding this if anyone knows. Still an amazing tutorial and I've learned a lot. Thanks again.

How to use it for movement character or jump or attack?

FIRST! KEEP UP THE GOOD WORK!

Very clean implementation! I'd love to see your take on something like behaviour/decision trees. Maybe a deep dive into the power of using both HFSM and BTs together. Especially to handle AI logic, as introduced and explained by Bobby Anguelov at this 2017 GDC talk (AI Arborist: Proper Cultivation and Care for your Behavior Trees) (ukposts.info/have/v-deo/iaGQrI5ogXmjxn0.html).

YES! I got this video just when I needed it!!! Thank you! I'm using Godot now, but I'm sure it'll apply over

Amazing video! What is the theme that you use for Rider ?

I think this looks cool, but feels like the update method is a bit heavy, checking for state every frame. Could you make a video about the same topic, but using events for state management? Update could still be used to run state.update logic I think

Very cool video !! It's super cool to have content like this ! I just got e little problem, i'm new in state machine, and I don't really know where i'm supposed to put the logic when a state is Entered. For exemple i have my P_StateMachine wich derive from the StateManager and i have a couple of Inum, "Normal, Stun, Sequence " and i would like to do stuff when the stun state is entered like stoppin my player from listening to the inputs. If someone could help me with it, it would be very kind of you !

Thanks for the video, it was very helpful! I followed along with the code, and when I went back into Unity, I got these errors: Assets\Scripts\BaseState.cs(5,56): error CS0246: The type or namespace name 'Enum' could not be found (are you missing a using directive or an assembly reference?) Assets\Scripts\StateManager.cs(5,75): error CS0246: The type or namespace name 'Enum' could not be found (are you missing a using directive or an assembly reference?) Assets\Scripts\StateManager.cs(7,53): error CS0314: The type 'EState' cannot be used as type parameter 'EState' in the generic type or method 'BaseState'. There is no boxing conversion or type parameter conversion from 'EState' to 'Enum'. Any tips on how to solve this problem would be greatly appreciated.

Can you do this for an Idle, Walk, Attacking state Machine?

Very good content, but the switch between light and dark presentation burns my eyes :(

Wait.. Abstract classes? Inherited classes? Isn't that more or less a scriptable objects? I think this will be great to be implemented on a scriptable objects

Now make it hierarchical 😄😎🤭

Awesome tutorial, but do you have a simple example of how this is best implemented?

Ideally you want to do away with enums and just make NextState return a BaseState. BaseState is also against C# naming guidelines. They’re just guidelines of course, but generally calling something “Base” is less useful than being more verbose about derived classes. Example: Truck : BaseTruck vs PickupTruck : Truck

So I am having an error The given key “Idle” was not present in the dictionary while I was trying to make a player state machine. How do I add key?

Hi, Im looking at this tutorial for two days straight, and still cant figure out this: I made PlayerStateMachine (PlayerSM) with enum EPlayerStates that is passed as generic. If I made PlayerIdleState, that inherit from BaseState. How can I in GetNextState return EPlayerStates.Walk, if i dont have access to EPlayerStates in PlayerIdleClass? I tried passing whole enum from PlayerSM when making an instance : States.Add(EPlayerStates.Idle, new PlayerIdleState(EPlayerStates)); but it cant be done. Can u help me find out what to do here? Also i dont wanna pass 4 arguments for four different states and store them so i can return them.

Hello iHeartGameDev. I like to make games with lots of movements and i struggle a lot while creating such games and i dont think its becuase i am unable to solve maths or anything, I think am not using the right coding pattern or the best coding strategy for this particular task. So Can you please tell me what coding pattern or coding structure i should use for making a game with lots of movments. And By the way what coding pattern big companies implements for lots of movement in game?

Thanks for the great content, for the next videos please zoom in the code editor a little bit, too much space on the right side is wasted and it's hard to read the codes with smaller screen.

Explain where you put the "EState" enum. Because it gives me errors.

Nice work, but state machines doesn't work so well in parallel processing situations. How do you manage concurrency between several processes calling enterState at the same time? Which of those is gonna win the authorization to change an entity state? A good exercise would be a multiplayer game where bullets from two players hit the entity (headshot) at the same time: could you ensure that the entity state change from "living" to "deceased" will not be done twice? Will you be able to identify which player hit the target "first" to give points to him/her ? That's why i generally prefer messaging queues instead of state management. Most states csn be procedurally generated from atomic values like "life points" when needed instead of carrying them over with each entity.

i found it quite confusing for godot, i dont know how i can implement that in Godot because if i make abstract class then i cant inherit from "Node" (basically cant inherit from monobehavior) thus cant have "awake", update etc. Which i dont know how to enter state in the concrete etc (the old tutorial does work great, i hope i wont find issues with that old video state machine but it does look promising)

I have a question is it in animation open source for sign language

Any chance you can showcase some states like idle walk etc

Could you do a video on the GOAP algorithms and how to implement that

Only thing I would really change is adding a getter for CurrentState. CurrentState is too useful of a datapoint to not have accessible. Let's say enemies, you make a sensor script to do vision/hearing, and the SensorScript can have a higher or lower range based on what the current state is.

Do you have a video about how to do AI Movement with animation?

Im having difficulties in trying to use your Better Statemachine in order to create concrete states. I am new to statemachines and do not have any experience in how its done using other methods. Can anyone give a sample of how a concrete state should look when using his method?

As dumb as this question might sound, could someone apply this same logic withing the godot C# pipeline or do they need to do a whole lot more adjustments?

I have followed this but I am just lost on how to implement this using what has been set up. I just cant seem to wrap my head around it. Any help?

8:25 - You imply that Unity will execute Update methods parallel which is not the case as far as I know. Even if Unity did that, creating a simple boolean guard is not sufficient for preventing race conditions among threads.

Is there a video you made explaining how to make animation specifically for you, which means that animation is not available on the internet , for example , and you want to do this