An 80 minute video on a design pattern?! It really is Christmas, thanks Chris

People don't understand the hard work puts for +1h explaining design pattern + editing, thank you 👌

I usually watch various tutorials, so I feel capable of giving a "competent" judgment: you have excellent presentation, comprehensive, organized, straight to the point, more than valid expertise, but what struck me is your enthusiasm and eagerness to convey competence. You deserve a like and a subscription. Thank you for your effort.

only with these videos I've aced the design patterns exam . Thank you .

Can I just take a moment and appreciate your efforts here! You made design pattern really understandable for me! Hats off to your efforts 🙏🤗 Wish you get everything required to be able to continue this series as well. Take care Christopher :)

36:00 definitions 51:23 code

that was a GREAT video! Chris, we're missing your videos on design patterns and different topics really bad! I hope you can find more time in the near future to help us learn more and become better software developers. Much love!

Watched at 2x speed; it's doable as I've some pre-existing knowledge of this pattern and this video makes a great refresher. Thank you very much.

There was a similar example in a textbook I used to teach Java which used three states LOCKED, UNLOCKED, and ROTATING. The transitions were "payment" for LOCKED --> UNLOCKED, "push" for UNLOCKED --> ROTATING, and "one revolution" for ROTATING --> LOCKED.

"Replace a conditional with polymorphism" - this will be my new favorite quote from the entire design pattern playlist kek ~ (the same concept used first in composite pattern)

You do a very good job in visualising these problems. Thank you, I'd be in trouble with my design pattern course without you.

What a explanation 🙌🙌 guys if you are confused whether to watch or not seeing the video duration, just give it a try. As otherwise you will have to waste double the time while reading articles

Nice one, but I disagree with passing the gate reference. If the interface for a state declares that an action causes a state to generate a state (e.g return GateState), you can avoid passing references to the gate itself, and from your gate call the action on the state to return a new state, and assign it to your ivar locally. Other than that, I like this playlist. For each pattern, I created a swift playgrounds version for future reference. I wasn't aware I was using so many of them :) Keep up the great work!

This is a really nice tutorial. Please keep it going. I am kind of addicted to your videos now.

you are perfect, i have only a few hours before exam i tried to watch 2x speed but it is still perfect because of body language, fluently speaking, diving into everything with clear explanation. need to say that i am still trying to learn english but i understand whole video. THANK YOU A LOT FOR YOUR EFFORT AND AMAZING JUMP CUTS.

Hey man, I just found your channel. Immediately I knew I liked you, and it took me a while to figure it. It's cuz you look like Antonio Banderas! Your energy also is amazing! So much alive and warm :) I'm a smart guy, but as soon as I build a game that has all the basic elements . . .I get lost in the jungle of the code. So I started reading about design patterns. Well, my friend. You're the first one that I can follow! And even understand to that point that I can really see what you drew on your whiteboard as beautiful! Please keep making such simple videos and stop for so many explanations! :) :) :) Thank you man! p.s. Headfirst book sounds like a thing for me Love from Croatia!

I've studied your videos for a while, and come back to them. But, I find it's only when I actually need to use a certain pattern that your videos make sense to me. I need to use the state pattern for game development and this video has been a God send. Thank you so much.

the best patterns explanation I've come across so far

I have been searching for Design pattern tutorials online like forever, to find something that can be more relatable to the software systems. But all I ever find are Ice cream, Pizza, Burger examples, which makes no sense what so ever. Thank you so much for all your efforts and making sense. I feel I am a better Software Engineer than I was 1:20 Hrs ago.

I watched tons of video about DP, your DP playlist make you special among the bests Chris!

Only 72 comments? Here one more to appreciate your hard work and effort!

As suggested in some comments, I would rather return the next state to the gate, from the states "action" methods, something like "nextState = currentState.actionPerformed()" (instead of a void return)

I really like how you explain things (and sometimes go to other related things and go back). I thought I was the only one who explained things in this way! Thanks a lot for your videos.

The way of your teaching is very interesting and helpful. Thanks for your effort.

This has been very enlightning! Very well explained with the exact amount of detail, thanks a lot!

Thank you so much for providing so many awesome videos. Even though I am unable to fully understand or master each every pattern, but you gave me the courage to dive deep into OOD. I will definitely read these two books again. Thank you !!!!

Good explanation of the concepte and theory of the State Design Pattern, when rarely found in KZfaq. (y)

Dang! This is the best of ALL the videos so far! I really thought I just knew this pattern inside out... and still the devil is in the detail... I'm saddened that it doesn't have more views, ALL developers should be forced to watch this :)

The best explanation of this pattern in the internet still 2020

great sound effects. the "boop" sound is to die for.

Amazing explication. I loved it. Congrats Chris. Great video. Thank you very much.

It is a very informative content, presented nicely. I like your videos and the way you explain things. Keep up the good work Chris 👍😊

Regardless of mutability, I would not store a Context (Gate) reference on all States. That creates a stronger bind between the Context and the State than simply using the context with needed (and then discard). With this in mind, I would simply pass the Context to each of the State interface methods so that the concrete State could then use the context to set the new (current) state.

I will be your patreon if you start making videos again, you have my word.

I really like the idea that sometimes I don't get it the first, but then he tries to rephrase what he's saying or puts in a different way or with a different example, and then it starts to make sense to me. That's a lot of effort in explaining. He should become a professor or something.

I love this entire series. Fantastic!

i literally love you for these videos

Great teaching and information. Thank you very much!

Thank youuuu sooo muchhhhhhh ! your the best way to understand the concrets concepts of DP

Hi, many thanks for the video I' ve learned a lot, appreciate that. My question or maybe suggestion, would you consider to change the names, to turn the names of the states e.g. OpenGateState => GateStateOpen, ClosedGateState => GateStateClosed etc. because int this way it's even more clear that they belong together.

Thank you so much for these videos!

Best design pattern videos 🙌

This was amazing, I learned alot. Thank you Christopher :-)

looking fierce bro! Thanks, you explain very well. ….. 25 more minutes in and damn even more impressed. I subscribed, thanks for teaching,

Once again.. another Great Video . Kudos to you.

Really really good tutorial. Greetings from Poland:)

This channel is such a blessing. Thank you so very much Chris.

Hi Christopher, first thanks for your explanations it helps a lot. I did not check the other comments, then I will give you my question (4 years later ^_^') Each time a state is changed by a handler by the changeState method. And through this method a new instance of State object is created. So here is the point: how the older state instance is deleted ? I suppose it depends of the languague we use but in some examples, a static instance is used

It's great how you can describe things on the desk, but I guess the coding part can be done in textEditor or smth. With splitscreen so every class would be visible to a viewer at the same moment of time. The code would be much cleaner and readable thus. Means = more understandable

Thank you so much for your passionate work!

One of the best explanation! Thank you very much!

I like It a lot, a bit longer than expected, but perfectly understood, this is a pattern very used in React, but this video is very useful to use It better

Very useful and clear even for a soil scientist like me!

Hey Chris. Thanks for these invaluable content. One request. Could you please do a video on Interpreter design pattern? Thanks mate.

Question of the day: Have any examples of where you successfully used the state pattern?

> Interesting: we've modeled the state and how it responds to different events, but we have not modeled how the events themselves are triggered. That will be the business logic tied up with the idea of 'Context'.

You are a great teacher!

excellent video, you have the gift of teaching! subbed

Thanks!

Thank you, dude! Useful and comprehensible tutorial)

last repetition before exam, great job :D thanks

Now it`s all clear, thanks !

Thank you so much for the wonderful explanation Chris!! Looking forward to more design pattern videos from you... for Builder/FlyWeight/ChainOfResponsibility/Memento/Mediator/Visitor may be? :)

Great work 👏

I've devoured your entire playlist and now I'm sad cuz there aren't any design videos of such quality and engagement on the internet :( What about resuming the series?

Would it make sense to implement the singleton pattern on each state so that we do not need to instantiate thousands of states and just use the one we need ? You would pass the gate as an argument for each method but you would only have a single instance of each states and gates would still use the one they need individually. I know you've said that we should avoid using the singleton pattern but if the object instantiated is just a library of methods there's no reason to duplicate it... is there ?

great content, used to watch your videos years back, and now again. i noticed a small mistake but its not a big detail: in 7:10 u mention that if youre in the openstate and you receive a payOk message you stay in the Openstate, but in 58:11 youre giving an example for when youre in the openstate and you receive a payOk you close the gate. i think you accidently overlooked it

Very good stuff. Thanks man!

Pretty good explanation. Thanks Chris. May be this needs a better example since 2-state machines don't really need a State Pattern but a boolean and we may be abusing the design pattern (aka Design smell) in our code.

I have a doubt here. 1) While transitioning states, we are always creating a new instance of next State object. Is this a good idea ? 2) Is it possible to create all possible State objects just once and store it in the Context Class (Gate class here). Since we are already passing the Gate class to the GateState class, we can just get the next State object from the pre-created objects instead of creating a new one every time ? 4) If yes, can you give a correct way of implementing above thing.

Thank you!

I'm feeling weird about the idea that the state provides a new state to the state machine. Shouldn't there be a contract (ie. interface) between the state machine and the state where the state can use GoToOpenState() rather than creating a dependency between the concrete OpenState and CloseState? I mean if I'm a state, I shouldn't be responsible for instanciating the next state, rather I should tell the state machine that now it should transition to the state Open, however is has been defined.

Thank you for your explanation. It was especially useful to hear about state diagrams and to see them used in the explanation of the UML. Your method of repetition seems to really help link your different parts together. I did have one question that I may attempt to experiment with myself and that is why a concrete state object wasn't returned from the action/message handler methods and used to set a reference in the context?

This is amazing, really great Thank you

Your videos are amazing. I enjoyed every bit of them. There is not a lot of good tutorials on advanced OOP on KZfaq. Can you please consider making some?

I like this video will check your other videos for sure

Mixed feelings. After I watched this video, I felt that injecting the Context (Gate) into the State is unnecessarily complex. It would be simpler and more explicit to return the new State from each handle (and simply return "this" if we stay in the same state) and the Context request methods are responsible for applying that returned state. Then I realized that the pattern is not only about states and transitions; the states also do something for each handle, that is, they manipulate data. And this data resides in the Context (preferably in a third class, say, Data). So it is necessary to inject Data into the State. And I think I'd prefer to do this as an argument to the handles. So, to sum up, I think I would prefer to have "State handle(Data data)" methods instead of "void handle()". Do you see any downsides? PS: So far I have implemented all my state machines using enums and switch(). I wonder if I really try the State Pattern next time.

wonderful series!

I think you have an error, or may not, correct me if i'm wrong but, When your Gate is on state open and you receive the method payOk() you should stay on open state, right?

I think that this payOk() method in OpenGateState should be the enter(). Thanks for your work.

If you wanted to avoid mutation and dependency injection, would you just make the interface methods be of type GateState and say state = state.enter(), for example?

Much appreciated 👏🏽👏🏽👏🏽👏🏽👏🏽👏🏽👏🏽

Simply Superb

I have a question, considering the initial discussion when we decided that in the OPEN GATE STATE if we try to pay again we would remain in that state (even if the payment is succesful or not), the concrete implementation is ok? Im a bit confused

brilliant content!

learned a lot from this video, Thank you... I have a doubt, why cant we return state itself . How about changing player state outside of the state class, e.g gate.state = gate.state().enter(); - - - -- -- - - in our main class

This was good, I learned alot. Thank you!

wow this is an amazing tutorial thanks man

Really aweaome way of explaining concepts. More than that tge passion you show is tremendoua. Thanks for sharing uour knowledge. One question i had was ...why is pay part of gate class after paymentbdoes not happen on a gate. Having payok makes sense but not pay. Isnt it?

soooo coooool thank you

Love this, thank you!

got a deep dive into it .

Wow! this is a jewel :) I would be using state pattern with my upcoming project and this video explains everything on topic. Excellent video. Keep the great work up (Y) I would like to hear your opinions on Inversion of Control and Dependency Inversion principle from SOLID. I am super confused between these two and can seem to make distinction between them. They look same to me

it was 09:36 and i think i know how to make it. is it brilliant btw.

Hi Christopher, I have a suggestion regarding this pattern. I think methods in State interface can be of return type State instead of void & inside gate class or the context, whenever delegating to the Concrete State Classes we assign the return State like - "this.state = this.state.payOk();" and (return this) or create the required ConcreteState Object in Concrete State methods. and this adds only one assignment in every method of context. BTW Awesome Videos, Best Videos on OOP & design patterns on Internet, & lots of Thanks from India.

Hi Christopher, great videos and playlist. It helps me a lot to appropriate design patterns. About the State Pattern, it kinda looks like the Strategy Pattern as each state has its own logic, right? I would define the State Pattern as an evoled Strategy Pattern. Do you agree? Do you consider make a new video in this playlist to explain the difference(s) between these two? Thanks again :)

Great video and channel I like it very well

Dear Sir, at 1:02:47 inside the OpenGateState once we pass payOk() shouldn't it stay in the OpenGateState only? Why have u passed the changed state() and changed it to closed state? ClosedGateState will only come if I pass enter() in the class definition of OpenGateState? Kindly clarify.

Great video! I have been struggling to understand State Pattern but you made it really clear! I’m not very sure but the sample code you provided seems to be impossible to instantiate (apologies if I’m wrong) The reason is that the Gate class requires GateState object in the constructor while GateState requires Gate object in its constructor. It looks like circular reference, would it be possible to instantiate? (I’m gonna test it out when I’m available)

very nicely explained...thanks a ton for this :)