Studying for a Software Engineering exam right now, and Design Patterns were explained so horribly. You are a savior!

As a hobbyist web developer (mechanical engineer), I am loving your design pattern tutorials with realistic examples!! I have been searching tutorials/examples on the internet, including here on KZfaq, and have not seen anyone that can be compared to you. Thank you!

In your PlayWithRemote class, I think it's better form to, instead of using: TurnTVOn onCommand = new TurnTVOn(newDevice); use Command onCommand = new TurnTVOn(newDevice);

Thank you :) I'm always happy to hear that I helped. Thanks for taking the time to tell me the video was good

You're very welcome :) I cover all 24 patterns by the end

I'm learning Design Patterns with C#. I love the clarity of that video.

A true technological breakthrough... A TV that can change volume even when it's off!

Firstly Thanks and appreciate your effort for us. I think, by this time, you'd have already created all the videos. It would be really helpful if you could explain the problem and then implement the particular design pattern which would make these tutorials stay in our minds forever. Once again Thank you!

Hi Derek, great tutorials. Maybe you can add complete class diagrams of the programs you create during the video's.

I am a student of Computer Sciences and your video tutorials have really helped me in preparing for my exams. Many thanks...

You just showed what hard work does ? Improving others life. You deserve more subs and great respect. ❤❤❤

This entire series is AMAZING! Thank you so much for providing this for free to the world!

Thank you :) I'm glad you enjoy them

I really appreciate the teaching style, it's so easy to follow along. Thank you Derek Bananas.

Design Patterns are really just guides that an advanced programmer can use to write clean understandable code. They aren't recipes like you are more then likely use to. Once you learn basic syntax you eventually will see that programming is a form of art and you must work to truly master the medium. At this point I don't think there are any real rules except that code should be flexible and understandable. Patterns help you do that.

You could go that route. I have always looked at these patterns as guides rather then as set in stone rules. For the most part though, I followed the GOF rules when I made them in this tutorial

Thank you :) If I'm understanding your problem, it sounds like method overloading would solve it

You're very welcome :) I do my best

I love so much about this video. Articulate, confident, prepared, informed, quick, simple. Thank you Derek Banas. I see you're doing pretty well on the Tube and wish you more success in the future.

Thank you Derek! I am also studying right now for my software engineering exam!

Don't know what to do without your tutorials! Thank youu

You're welcome :) you can solve many common problems with design patterns

I like how this example is also an example for one of the SOLID principles which is the Single Responsibility Principle and that's why I don't think its a negative that you have multiple classes because this reduces the dependency of your code.

Uoooh!!! The TV is turned off, but you can still turn up the volume!! Very powerfull the command pattern, cool!! By the way great tutorials!

This is awesome! AWESOME!!!! I have watched probably all your design patterns series, but this is by far the coolest! I was wondering for a while about how on earth does one implement a solid undo functionality in an application, something as amazing as what Microsoft has going on with most of its office apps. This video is a huge help bro! Though it’s been 8 years since you made this, I would like to thank you a ton right now

Thank you for the video! In my class I just got thrown into many design patterns and client/server networking and a bunch of stuff I've never worked with. But you going through the code while writing it out helped me to understand this much better!

Thank you very much :) What would you want to see in a prolog tutorial?

Hey Coach , this time FASTEST FINGER FIRST YAY !!!!!!!! Thanks for sharing this and stay blessed as ever .

I'm going to cover Java EE and the associated technologies in a separate tutorial. Pretty much every request I've received lately will be covered in that tutorial including anything that has to do with networking. Don't worry I'll get to it :)

Great explanation and code examples. I've viewed a few other videos and articles but your the first one to make it click (pun intended) in my mind.

in .NET commands also have a boolean CanExecute property that can be used to enable and disable controls automatically in a bound UI. Great explanation.

As always with your tutorials: a pleasure to view, learn and recap.Deep respect for this great work!

Thanks for this. I understand the pattern, but I still don't quite understand the utility of it all. What are the advantages of using this pattern?

Clear speaking, and a thorough explanation. My only critique is the order in which you explained it. It would have been easier to understand if it was explained in a top down manor rather than a bottom up. For example, the code that supports the pattern was written before the code in the main method was written, (which is the direction I code in when I have the design settled on). However, when doing design, or learning things, I find it is much easier to start at the abstractions first then work down to the details, (the code).

Keep up with good work! Not only have you helped me with my test, but I have actually learned something here o/

These videos are gold!!!

Sorry about that. Here it is kzfaq.info/get/bejne/nrh4oauol7K6koE.html It is my Code Refactoring pt 13 tutorial. It covers the command pattern again

Hi, great video! thank you for sharing. Sometimes I think why encapsulating is needed in the first place. Why can't we just work with device object. pass it and call the method, that we want to call. The answer is: to make code less coupled. When we create a command, the interacting part is represented in a small functionality. The end-user of command interface don't affect or depend on original device code. In the presented code, device is created by ourself. But in practice, device code can come from third-party libraries. We may not have control over them. In the examples of the video, it may not be clear, because all the code is created by ourself and may be changed by ourself when we need it. And second benefit of creating command, that we don't change the original code of device. For example we don't force the device code to implement our custom interface. I hope this make sense

Hey Derek great tutoria, thank you! Maybe just one improvement would be to comment the corresponding UML name in the code class would def. help in memorizing

I love your videos ! My only small criticism is that your voice is super energetic at the start of the video but is a little monotonous when you are half-way through the code.

Some people don't understand that this is used to solve a problem that is commonly known. If you have not experienced a system that requires this pattern cool, but sooner or later when you start looking for solutions in complex systems you'll find the "patterns" useful instead of reinventing the wheel.

Thank you :) Sorry about the monotone voice. I normally do that so it is easier to edit the video.

I got the concept but i didn't really understand why didn't we just used the method of the electronic device straight up. Instead of using a new class just to invoke a method in my original electronik device why didn't we do something like myElectronicDevice.volumeUp(); ?

Dude, my software design professor's got nothing on you, thank you very much

I'm glad you have covered Command and Memento, thanks!

Two things: First, the "Command" pattern just turns a method/function into a class (in your example, a class of the same name as the method it calls) for languages which don't support passing functions as arguments. It's very heavy on the use of wrappers. Second, your DeviceButton class is very similar to the Command class that it makes use of, in the sense that it just calls a pre-determined method of an object which you give it at instantiation (just like your Command subclasses)

Very good explanation........... But please if can tell more as where it should be used and where not with some real life examples... Or is it only best adapted for Undo feature only?

Fantastic tutorial - this helps quite a bit!

Siete i benvenuti! Quante lingue conosci?

Because TVRemote is a utility class and it isn't meant to be anything else

I have followed some of the tutorials. Its really great!

The homework is totally optional. I only provide it because I'm asked for homework all of the time. I think the solution is pretty simple though

Great video overall. One question : why have you not used interface segregation principle for device interface (on,off) and (volumeUp, volumeDow) ?

Great Video!!!.One Suggestion: At the end of each DP video if you can add examples from Java APIs then i think it will be very helpful.

Thanks for this video, very helpful. BTW, why do - class TVTurnOn has a member ElectronicDevice? My Idea was - TVTurnOn should have a Television member, because the class TVTurnOn is already for TV and not for other type of ElectronicDevice. Is my idea is correct? and if not why ElectronicDevice makes more sense to use? Many thanks for the answer. newbie here :)

As usual, it is a masterpiece. Just wondering, is it also called "call back"?

Very helpful video keep up the good work man

Thank you Derek, I've studied all patterns through your videos and I really understood them well. I have one question tho regarding this one. What should I do if (for example) the TV needs to know which "remote" executed the command? Should i pass it as argument when calling execute or is it better to pass the object by constructor? If the latter, then how can i know the object already when constructing the command? Greetings

Why is the abstraction required with an extra class DeviceButton ? Arent we over complicating things a bit. Also, I would be interested to understand, an use case where you used this pattern. Good stuff!!!

Great tutorial. I love all your tutorial you are simply awesome. Could you please cover these topic as well at your earliest convenience:- Enum Enum with complex problems example of Enum with Design patterns Json Object Mapper, JSon Node Restful Services with Java

Sorry if I'm misinterpretting this, but is the Command Pattern like the Observer pattern or like using Delegates? Like what's the difference between this and having the ElectronicDevice interface (I guess it would have to be a class to inherit from in order to use delegates/events) and saying class TV : Electronic Device { base.onTurnOn += TV.TurnOnTV; } Just curious. Thanks.

Congrats :)

I have to learn all of these patterns in 3 days for my teacher. I love Hungary xD... and it's just 3/13 th part of the subject. Exam is coming. I'm lucky I can watch these. Only these videos need no observation cus it has an aim so i can guess the details by iq so I don't need to be observant :))

Thank you, I think I understand the command pattern bit better now, but the undo part is just messed up as undo doesn't work like that. I guessed you should have used some registry, record the commands and then replayed them backwards in the undo mode?

So it's basically having a class that acts as a command rather than an object?

As always an awesome tutorial. I have a little observation here. Insteed of TurnTVOn, can we rename it as TurnDeviceOn as its a command and can work on any receiver.

Clear explanation thanks.

Hi Derek, First you do good work! Can you please explain to me the difference between command and strategic patterns? They both looked so Identical. Thanks

Seems to me the main parts are simply the Target, Command, and Invoker. A Target obj - which could be any device which has its methods. A Command - which contains a device, and the execute method. The execute method just calls a method in the device. Invoker - is just an object that contains a command, and a method which calls the command execute method. Examples. Device - TV, Radio, Robot, Vehicle, Lamp, fan, Phone, Weapon Command - on, off, change settings, move, fire, Invoker - button (press), switch (toggle), lever (pull), knob (turn), listener (event),

very helpful tutorial. Thank you very much!

Why do you even need polymorphism when creating a class as specific as 'TurnTvOn'? You might as well make newDevice of type Television instead of electronic device, right?

Fantastic tutorial, Derek! Good job! I have a simple doubt. In your video, you created a list of devices to turn them off all at once. Could I create a list of commands in my Invoker so that I add (and queue) commands to be executed later at the same time?

there's no specific pattern for a queue/circular queue, u can write the whole queue system itself in 1 class. only when you want to add items that are specific polymporphic types you could use a factory; or the observer pattern to show the first item in the queue

Great Video. Simple and very effective!

Thank you :) Yes a stack would be quicker

Hey Derek, can you do a implementation of the Command design pattern in a real life situation such as in a Command design pattern in a Model View Controller?I did an assignment where I had to do just that in a paint program and was honestly stumped. Love your videos :D

Simply, but great explanation. Thanks a lot ;)

I have a few questions, with command pattern, there is always going to be a interface? Also you will use the command pattern for things you would like to turn off and on and that have certain levels such as volume and etc.?

I am not sure but I think this is probably one of the most used patterns in a microservices environment where you have to make interprocess communication.

Thank you :)

Great command pattern tutorial! I think I actually 'get it'. However, I'm still a little fuzzy on the rationale behind it all -- isn't this kind of pattern basically 'breaking' OOP concepts of state and action by converting methods into class objects? Perhaps this is why some of us have problems relating. It's one thing to understand that a bicycle object has gears (fields) that can be shifted (methods). It's quite another to make the process of shifting them into a class object. Something just feels wrong about it. Thoughts?

Excelent class, thank you!

The undo for turnAllOff is not accurate because you're assuming that everything was on before calling turnAllOff. You should restore the previous state of the Electronic Devices.

I did the same in pascal, and actually works the way that was expected. Well done sir! @Delek Banas

hi Derek. great series. in the intro to this video you describe the primary use of the command pattern being to store a list of commands for later execution. but in the body of the video, the commands execute immediately. is it still useful to use command pattern if there is no need for delayed execution? and if so, what's the advantage? the extra classes seems a heavy price to pay if there's no need to queue them.

Very helpful , easy to understand, thanks Derek!

Thank you :) Yes you win the award for being FIRST today!

your video was really helpful!! can you post the uml diagram for this example please

Would it be better if you rename the class TurnTVOn to TurnDeviceOn, etc.?

At 10:30 why do you have to keep a reference to the Command instance in the invoker? Why not just pass that Command into the press() method as an argument and make the Invoker completely static?

I'd like ask, if it's a good approach to have the device return a value from it after it's executed or would that be another pattern I should look at like Observer or something?

The names of your classes don't make sense... It should be TurnDeviceOff instead of TurnTvOff... Also you're not coding to interfaces like you originally said at the start of the video. When you create a new Command you set the Command object to itself. TurnTvOff command = new TurnTvOff(electronicDevice);.

Why was the ElectronicDevice implemented instead of being inherited?

now i have an idea on how to do undo:) Thanks!

Hi, I find this same as Bridge Design pattern. Can you please explain how this is different?

Since Java 8 introduced default methods into interfaces, you can add the undo as an empty default method to the Command interface and avoid implementing it for every single class that implements this interface.

thats one funky way to do a method call

Great job !

Why you state the undo method as a specific feature of command pattern? It looks like it can be implemented in other patterns. Thank you.

When you say "Object object; Object object2=new Object; object=object2" It assigned the address of object2 to object and you can use it normally?