Strategy Design Pattern

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Here is my Strategy design patterns tutorial. You use this pattern if you need to dynamically change an algorithm used by an object at run time. Don't worry, just watch the video and you'll get it.
The pattern also allows you to eliminate code duplication. It separates behavior from super and subclasses. It is a super design pattern and is often the first one taught.

[@derekbanas]

Learn in One Videos for Every Programming Language Subscribe to Bookmark them: bit.ly/2FWQZTx C++ : kzbin.info/www/bejne/iKbFXn2pn7Kbjbs Python : kzbin.info/www/bejne/hGXQdq18ec-kqqM Java : kzbin.info/www/bejne/pF7bcqSZd6iqqZY PHP : kzbin.info/www/bejne/bYWpYWOef65qbrs MySQL : kzbin.info/www/bejne/r4HYZ6SMasesq5Y JavaScript : kzbin.info/www/bejne/nJvYapyfbb6mfdU C# : kzbin.info/www/bejne/oprWmqqLj6-Lp7M HTML5 : kzbin.info/www/bejne/oXXce4FtprZ4iqM CSS3 : kzbin.info/www/bejne/eYbbeZKojLh8Z80 JQuery : kzbin.info/www/bejne/eIi7mJp4YrlkoLM TypeScript : kzbin.info/www/bejne/Y4G1kIunjJ59gLc ECMAScript : kzbin.info/www/bejne/gJLOoJxmfJ2feMk Swift : kzbin.info/www/bejne/mnzEoJ2Fj5KUsJo R : kzbin.info/www/bejne/qWSpoK2Mm8lqp5Y Haskell : kzbin.info/www/bejne/ZmPCeWaCn9aAqJo Handlebars : kzbin.info/www/bejne/annYcqGDa8dlmpo Bootstrap : kzbin.info/www/bejne/naKydqKLh5qFfsk Rust : kzbin.info/www/bejne/i2Kod5p5g7F3eJo Matlab : kzbin.info/www/bejne/hIS2hZ6hgLeUmKs Arduino : kzbin.info/www/bejne/h4DCe5-wZtajetk Crystal : kzbin.info/www/bejne/eqmpgWCNn9anqcU Emacs : kzbin.info/www/bejne/f5LKk6lvbJl6orM Clojure : kzbin.info/www/bejne/mZqqqnuhedqDd6c Shell : kzbin.info/www/bejne/nqjVn6CHqtKnhtk Perl : kzbin.info/www/bejne/jXbKmXyOqJ15bMU Perl6 : kzbin.info/www/bejne/omHdgaqenLyHna8 Elixir : kzbin.info/www/bejne/pnOxgJSsh9SBgpI D : kzbin.info/www/bejne/qKi9d4ekm56Verc Fortran : kzbin.info/www/bejne/lZCVhpp8g76anJo LaTeX : kzbin.info/www/bejne/jJnQnH-ohM9_qdk F# : kzbin.info/www/bejne/mWjIf3eAg5xobrc Kotlin : kzbin.info/www/bejne/fpDSeJxuqtp3pqM Erlang : kzbin.info/www/bejne/f3bLqJZoppatfZY Groovy : kzbin.info/www/bejne/eGqbm5Zuncmob8k Scala : kzbin.info/www/bejne/equppWOPoL-ibq8 Lua : kzbin.info/www/bejne/n37ElKuQhrKDjtU Ruby : kzbin.info/www/bejne/epvManSCeMyZpq8 Go : kzbin.info/www/bejne/eXechGeHj9qJaZI Objective C : kzbin.info/www/bejne/a5bWgqSQfq9rack Prolog : kzbin.info/www/bejne/iarOqYqme9yAfdU LISP : kzbin.info/www/bejne/r562ometfdekr7c Express : kzbin.info/www/bejne/rnWmfJaEd6umq6s Jade : kzbin.info/www/bejne/omakiZaOdrVnqJo Sass : kzbin.info/www/bejne/rauWnHiigcd4fqc

[@neostarteon9718]

An example of this pattern with Dependency Injection would be great.

[@MohammadMNajar]

Can we get a tutorial on Spring Boot and Kafka?

[@apoorvwatsky]

jesus, what do you not know?

[@Daedlues]

This video is amazing because 1.you supplied code 2.you tried a wrong approach first which made me think why using this design pattern is important and when to use it 3.learning by example and my diagram at one video 4.your teaching style is clear ( little face paced for a beginner like me ) thanks very much i really needed to learn patterns

[@derekbanas]

+Daedlues Thank you for the nice compliments :) I'm glad it helped.

[@topogigio10]

@@derekbanas Sos un fenomeno Derek!

[@todarfclips]

For someone who's not a beginner like me, all those points hold true but his speed is amazing. It's exactly the right pace.

[@DatzAdam]

He also has magical powers by making a dog flies, amazing!

[@Tomas970506]

For my perspective and point of view. This tutorial is bad because he shows a bad way to code and then does everything on top of it. For a begginer it might be hard to grasp what is where.

[@alex26toma]

I like how you explain the bad practice code before presenting the design pattern. This way we know when to use it.

[@derekbanas]

Alex Toma Thank you :)

[@derekbanas]

You're very welcome :) Yes it takes a while to learn how to properly use patterns. Eventually programming stops being a set of commands and rules and instead becomes an art form in my opinion. With a bit of practice you'll soon start making master pieces

[@derekbanas]

Yes you can often use an Enum in this situation, but it will limit flexibility which is normally what you aim for with most design patterns

[@slidenerd]

i thought i would come revise my design patterns in java since its been quite some time and guess where I landed :D :D :D fantastic one mate,

[@derekbanas]

slidenerd Thank you. Nice to see you :) Keep making those great videos!

[@derekbanas]

You're welcome :) I can't wait to cover C++ and the differences that occur with these patterns. They are very similar as you said, but there are slight differences. The same is true with C#. I'll get to it as soon as possible. i promise to cover C and C++ as completely as I have done with Java

[@derekbanas]

I'll cover that in future tutorials. The short answer is that it depends on the situation. The object oriented analysis tutorial is in the works. By the end I'll cover everything oop. Thanks for watching

[@derekbanas]

Bog vas blagoslovi, kot dobro. Hvala

[@vikashverma9]

Where can I get PPT used in this video?

[@derekbanas]

Anytime you need to restrict a class you would need an abstract class over an interface. An interface really doesn't have any rules. So for example let's say you had a class that represented a printer. You know you'll have to stop printing if there is no more paper, or ink. That will always be the case no matter which printer you use. So an abstract class would provide those limits. Does that help?

[@heradsinn]

Great video and great series. Two questions: 1. Would you care to elaborate about 2:49, "Avoid Interfaces that Just Force Action"? 2. What is the literature on design patterns in general? Perhaps what GoF published back in the days, or maybe there are newer and better books about the patterns? Hopefully you still read comments 7 years later ;)

[@_timestamp]

Nope, he didn't read this comment

[@richardrisner921]

1. That means you should not add an interface which merely forces yourself to manually determine what every single animal will need to do with flying capabilities. An interface might be more appropriate for an action which would have a distinct implementation for each class.

[@derekbanas]

Here is my UML Tutorial Playlist kzbin.info/www/bejne/hZymaHuBqc6NeZI I also have a Object Oriented Design Tutorial in which I show how I solve problems kzbin.info/www/bejne/nHu6Z2iNpJx8fqs Both are on my KZbin channel. I hope you find them useful :)

[@derekbanas]

It is awesome to be able to help people all over the world :) Thank you for telling me you are watching!

[@sakhawathossen2104]

it's 2022, Aug 1, I am watching this almost 10 years later . And it makes so much sanse. Thank you a lot for this video man. A true gem indeed.

[@derekbanas]

Thank you :) I’m happy it is still helping people

[@brianlaudrupchannel]

I realise how bad Uni lectures are. If i finish my Degree its because of KZbin.

[@derekbanas]

+billyblackburn87 I'm glad I could help :)

[@rodrigobautista3768]

I understand you men, I'm studying at ESCOM in México.

[@todarfclips]

@@derekbanas Yeah seriously I'm using your videos right now to study for an exam, my teacher spent a 3 hour course on 3 design patterns but you went over one in 11 minutes and I understood better.

[@ناصرالثقافه-ق5ز]

@@todarfclips vf

[@ramiiii]

Have you finished your degree?

[@derekbanas]

Here are all my UML tutorials and codes in one place newthinktank. com/videos/uml-video-tutorial/ I hope you like it :)

[@TheAdithya9]

Extremely helpful. Really well put, well designed and such a good example! At it's most basic level. Good editing too. I'm sure it must be hard to squeeze it all under 15 minutes.

[@derekbanas]

Thank you for the compliments :) I'm glad you liked it

[@MsPedroGomes]

One marvellous from our times is that we can simply search for whatever input and quickly find a highly capable professor like you, explaining a fairly simple concept in a much simpler way, in just 11 minutes, with a clear enough voice to be understood at 2x speed. Many others would take a 60 min class, or even more to explain the same. Thanks!

[@derekbanas]

Thank you for the nice compliment :) I appreciate it!

[@jotaene764]

You have the teaching gift! God Bless you even more than you have been till now! Thank's for the charity with the humanity by giving away all that high quality high valuable knowledge of yours!

[@derekbanas]

Thank you for the very kind message :) May God bless you as well.

[@ناصرالثقافه-ق5ز]

@@derekbanas in Flow

[@derekbanas]

I've been thinking about covering Extreme / Agile programming techniques. I'm just not sure if there is any audience for that topic? I don't particularly care about views, but I don't want to alienate every viewer. I'll probably do a overview video on the subject and see how people like it. I also want to cover Discrete mathematics because the Khan academy never covered it and it works perfectly with understanding programming.

[@RVCata]

Well...this playlist has helped me better understand design patterns than 2 years of college. You deserve many beers. Many many beers :D.

[@derekbanas]

Thank you very much :) I'm happy that I could help.

[@saptarshimitra1267]

I have worked as a software engineer for 8 years and then went back to school & started doing Machine Learning. But when I wanted to revise my old stuff , your videos were the best option. Thanks for the effort and yes! UML tutorial will be great as well.

[@derekbanas]

+Saptarshi Mitra Thank you for the very nice compliment :) Here is my UML tutorial kzbin.info/www/bejne/hZymaHuBqc6NeZI

[@1yanivyaron1]

Hi Derek, Thanks a lot for your channel, it helped me a lot in my job interviewing process. I owe you one ;-)

[@derekbanas]

I think the answer is that you wouldn't want to ever have code from flys call for any other methods. You could do most anything in regards to class accessing using java reflection. The whole idea of using composition is to lower coupling and make the code more understandable and extensible. If you start using code that does something out of the ordinary then it would make the code less understandable. Can you give me an example of why you would need to do this?

[@jrumiak]

At 3:12 you state that super class change shouldn't affect subclasses but later you left flyingType uninitialised forcing every subclass cunstructor to set it's value. Shouldn't you just provide a default?

[@matthewhartz9235]

Yeah, i think this is a bad aspect of the pattern. If you, as a developer, were unaware that you need to initialize this, you won't get a compile time error. Or, if you provided a default, at least in this example, you might have flying dogs by accident in production.

[@abhi4unme2002]

Instead of having variable initialized by default, we must have explicit constructor for initializing all the strategy variables in the class, all such classes should not have default constructor for them , which has variables of interfaces in them.

[@veganaiZe]

I think that the Strategy Pattern has less to do with Super vs. Sub-classing and more to do with being able to change/substitute algorithms at runtime. In other words: It allows you to avoid hard-coding one particular algorithm (or implementing several and using conditionals to select between them) at compile-time and, instead, dynamically select the most appropriate at run-time. The Strategy Pattern basically lets you implement behavior (ie. an interface), where ever you find it most appropriate, and then it allows you to easily change that behavior. So for instance you can implement an I/O interface, which is initially text-only (all over), and then dynamically change it to a GUI interface; without re-compiling and without duplicating lots of code.

[@derekbanas]

You would use it with classes that are very similar. What you referred to is the skill one must develop after learning about patterns. Knowing when not to use a pattern is just as important as learning when to use them. I cover more on that in the refactoring tutorial.

[@abbos-alimirkhanov114]

Hi Derek Banas! It was a bit difficult for me to understand this line of code 'public Flys flyingType;' on 5:31th minute. As I understand it is field variable, and first we have to declare visibility which is PUBLIC then type, which should be some type like integer, String.. or void. After that goes name which is Flys, however in your case it is first visibility which is PUBLIC, then name Flys and then type FLYINGTYPE (I still can't understand what type is it) This line of code is breaking my logic))) However, I have not read about COUPLING which you mentioned in video.

[@derekbanas]

Abbos-Ali Mirkhanov By using composition to store flyingType I'm able to change capabilities at run time. We can then define the flyingType by passing it to setFlyingAbility and then tryToFly automatically executes the proper code without having to define anything at the beginning.

[@fakkkkkk]

Flys is not name, its type in this case. There is an interface Flys, and the variable flyingType is of this interface's type - Flys. The name of the field variable is flyingType..

[@KingMartinelli]

Flys is actually the type of the object and FlyingType is the name of the object. You said correctly, that it's a field variable, means there's nothing declared (no memory has been allocated). The point of this is, to define every class that extends from animal whether it can fly or not. Abbos-Ali Mirkhanov you should focus more on your programming understanding before you pay attention to design patterns mate

[@voltaireestrada7384]

shouldnt flyingType be private? maybe that's what he meant?

[@derekbanas]

That topic is both very simple and also very complicated. First off, you couldn't even participate in high frequency trading because those computers receive and act on information in less than 10 milliseconds. They just look for patterns, price discrepancies and trading errors and try to take advantage of them. Ex. If the price of IBM went up 2 cents it more than likely will go up another 1 cent so, buy it at 197.16 and then sell it at 197.17. Stuff like that

[@ronenfe]

I think the better way to implement it, is to create another subclass FlyingAnimal that inherits from Animal and let bird inherit from it instead of from animal.

[@Alex-ht1oq]

ronenfe Can't have multiple inheritance in Java. Sorry lol .

[@maximembabele]

ronenfe said "instead of Animal". so it is still single inheritance

[@paulrybitskyi1737]

On the Derek's "When to use strategy pattern" slide, there is a point called "When you need to use several behavior dynamically". Dynamically means at run-time. So, while you can create another subclass FlyingAnimal that inherits from Animal and let the bird inherit from it and dog inherit from Animal class, what happens when your dog, by some magical way, obtained wings and now can fly? If we went with your proposed way of doing things, then there is pretty much no way of telling the class that the dog can fly now. If we went with the strategy pattern as in the Derek's video, we could easily change the flying ability by passing another implementation. Although I admit that the example is a bit silly, the pattern definitely finds its uses in modern development.

[@derekbanas]

Composition is a major part of most of the design patterns, so I can't really assign that just to the strategy pattern. Design patterns in general try to add flexibility through avoiding high coupling in many ways that are quite similar. Inheritance should be avoided if at all possible, but above all else understandable code is the goal

[@StingJia]

Following the whole tutorial and type each line code manually. If anyone need the the source code, I upload them to: github.com/jiapengjun/designPatterns

[@TigasFMS]

Sting Jia He has it in his website.

[@sermilion_audio]

+Sting Jia cool, thanks a lot)

[@derekbanas]

I'm very happy that so many people around the world seem to be able to understand me :) the funny thing is that in my country I was often used to speak with people from foreign countries. I could always understand them as well. I'm very happy to be able to help

[@xpopcornx1747]

Seems like bad code when Dog is forced to set flying ability, a behaviour it shouldn't have.

[@vnie1988]

+XPopCornX I was thinking the same thing. It seems to me that creating a FlyingType class and slotting it in between Bird and Animal in the inheritance chain would be better. Dog would never have to know about it.

[@popuzin]

+vnie1988 but then dog can't fly even if it takes jet pack =) or if dog will mutate in some crazy flying doggybird )).

[@Gam3r979]

+XPopCornX You could easily set the default flyingAbility to CantFlys to avoid this problem

+XPopCornX I was thinking that maybe the reason it's called strategy pattern is because you're going to define the different strategies in order to implement (achieve) the method. If I implement a Flying interface I guess a more understandable example would be that in the noFly strategy, the animal boards a plane. So in that way, the animal can achieve or implement the interface, but using a different strategy. And there are many other strategies that could be thought of to implement an interface. The real world scenario that I'm thinking about with what I learned here is: databases. There are databases that write to a file (like sqlite), but other databases behave differently. So maybe a strategy pattern would be an interface to store data. We want the same thing (to store data), but the strategies are different.

[@l_u_c_k_y_7]

hahhahaha

[@derekbanas]

flyingType should be private I agree. I didn't call setFlyingAbility in a constructor because I was trying to be as flexible as possible. Well sort of I could have done other things to add flexibility in hindsight. Sometimes while focusing on the pattern I tend to disregard everything because I have this belief in my head that if I focus on optimization that it will confuse people. I hope that makes sense

[@BogdanBadulescuBadulescu]

it's : Flies ..

[@derekbanas]

For every case we can build a class that performs a certain action instead. You can see an example of this in my Abstract Factory tutorial. I define classes for all the potential weapons and engines for my space ship. We have a class implement an interface and then execute the right version of that method based off of normal inheritance. Does that make sense?

[@derekbanas]

Thank you :) Yes, I tend to make videos for intermediate programmers. Most everyone else aims at beginners so I like to be different.

[@derekbanas]

You're very welcome :) Yes you can create an instance directly in the methods attribute. It is a little odd I know

[@derekbanas]

You're very welcome :) If it helps make your code more understandable then do it. There is a misconception that there is only one way to use each pattern. Even the GOF book states that it is but a guide and the patterns should be adjusted based on need. I hope that helps

[@derekbanas]

It doesn't care that it is an interface. That is why the pattern is so great. The interface just does its job by allowing functionality to change dynamically while not effecting the super class. It may take some time to wrap your head around design patterns, but when you do you'll be able to write great code. It took me awhile as well

[@derekbanas]

Thank you very much :) I do my best to constantly improve. Sometimes in doing so I make a bad video now and then, but I think it is worth it. I plan to eventually make a tablet app for every tutorial series that will provide a quiz and animations to improve the learning process. I have started doing that a bit in recent tutorials. Most of the money I make from these videos goes back into making better videos. Thanks for the nice comment!

[@derekbanas]

Thank you very much :) I used to work as a software architect and part of my job was to train new hires and answer their questions. I'm basically doing here what I did with trainees. I'm not a professor

[@derekbanas]

Yes it is halfway between a regular class and an interface

[@derekbanas]

Yes you are correct. I wish I could have come up with a better example, but I wanted to keep everything as simple as possible

[@derekbanas]

I do use setFlyingAbility in the code sparky.setFlyingAbility(new ItFlys()) Yes you could set flyingType as private. I didn't do that only because I wanted to show 2 ways to set that value. Sorry about the confusion

[@derekbanas]

Hi Vishal, Thank you :) I'm glad you found it useful. I record with Camtasia 2 and I edit with iMovie.

[@derekbanas]

Yes a java enum is often well suited for that.

[@derekbanas]

Thank you for the kind words :) You have no idea how much I enjoy doing this. It is great to be able to help people!

[@derekbanas]

Thank you very much :) In the refactoring tutorial I spend a good amount of time answering design pattern challenge questions. That was a lot of fun

[@Jetisertes]

I'm a junior dev, and I picked up a lot of intuition along my programming years. I haven't heard of this pattern before, and I realized that I just wrote a piece of code yesterday that follows this design pattern after not being satisfied with a more traditional polymorphic implementation. Nice. Thank you for your work as a KZbin educator, I really appreciate your videos. Cheers.

[@derekbanas]

I have made a bunch of stock analysis tools and many patterns are involved. Yes the observer is very common. Sorry, but it depends on your program

[@derekbanas]

You're very welcome :) If you take a look at my OOD tutorials and the refactoring one you'll see that my number one goal is to write very easy to understand code. Very often we have to give up on some capabilities if we want to achieve that goal.

[@derekbanas]

Thank you :) I do my best to make the videos fast and compact. I'm glad you liked it

[@derekbanas]

Thank you for telling me you like them and that they help PHP programmers. I always wondered how well they would translate for languages other then java, C# and C++. Im very happy that they've helped

[@derekbanas]

Thank you :) I did my best to make it understandable by looking at it from a bunch of angles.I'm glad you liked it

[@derekbanas]

All methods should be marked as private. I don't always do that in tutorials, but instead normally leave them as default which is very much like private. Which methods are you referring to specifically?

[@derekbanas]

Thank you :) I have a Design Pattern, Java, etc. playlist on my KZbin channel. Sorry, if everything is a bit confusing because I have so many videos. I try to aim for 10 to 15 minute videos. I feel that that is the sweet spot for completely covering topics. I know I'm the only person making videos that long. Actually my videos start out at 30 minutes before editing. I'm working to improve them all of the time. Thank you for your insight :)

[@derekbanas]

Thank you very much :) I appreciate that. I planned on introducing UML along with this tutorial. The only problem is that I could easily make 20 videos on the subject. I can't guarantee it would be finished. Thank you for telling me there is interest in that tutorial though

[@derekbanas]

Sorry I go overboard every once in a while. Over the years you guys out there have taught me to always be on my toes and to not just flippantly provide answers to questions :) I'll see what I can do about covering the different unix shell versions and commands. I'd like to do it in an interesting way, which I can't think of at the moment

[@derekbanas]

Thank you very much :) I plan on doing a performance testing tutorial. I do that to a certain extent with the refactoring and algorithm tutorials. I talk about Big O notation and such

[@derekbanas]

Thank you :) I did my best to cover just about everything in one video. I'm always very appreciative of the kind compliments!

[@mostinho7]

Done thanks Todo move notes to onenote 9:30 UML diagram It’s a pattern to favor composition over inheritance. Use case: animal superclass, some subclasses fly and some dont. Instead of animal superclass having a fly method (where not all subclasses can fly) and subclasses overriding it to fly/not fly, and instead of having a flies interface that some subclasses implement and some dont (both these solutions are bad and duplicate the flying code or the non flying code), we can have a flies interface (but not have animals implement it directly). Instead we have “ability objects” that implement the Fly interface like ItFlys: Fly or CantFly:Fly. And animal superclass has instance variable (composition) of type Fly (the type of the interface) and subclasses set that instance variable to ItFlys or CantFly polymorphically. We can have many different types of flying, classes that implement the Fly interface like ItFlys, CantFly, FlyWings, FlySuperFast etc

[@derekbanas]

Thank you :) Yes programming to an interface is most always the best decision. I only use abstract classes when I must implement some nonabstract method

[@mostinho7]

Thanks this is the first video that made “favor composition over inheritance” click for me. I’ve always heard that phrase but now I see how it’s actually used.

[@derekbanas]

You're very welcome :) Thank you for watching

[@derekbanas]

Yes you can implement this in C++. You create a java like interface with a class that contains only virtual methods. Here is some information on abstract classes in Python python. org/dev/peps/pep-3119/

[@derekbanas]

It is very nice for me to be able to reach people all over the world! I'm very happy that you're enjoying the videos :)

[@spaarks84]

Thanks for your great post Derek. I really enjoyed your direct example of the Strategy Pattern emphasizing how you have decoupled any dependence from previous videos. Comments detracting from the ultimate goal of discussing the pattern in general, are no doubt valuable in specific business cases but the attention to detail about what is important to the pattern is what I find most valuable in this videos. For those who already appreciate the existence of individual business constraints within a given implementation, you're intentional quality of skipping particular details about , for example, how private or final a method should or should not be be is something in which, I ,for one, find much value. Your willingness to politely discuss via comments with others how your vagueness on certain points might be more invaluably clarified in particular situations is a cherry on top. Please hit me up if you want to discuss cleaning up your content a bit and syndicating for a good cause. I'm willing to pith in on other people's ventures and I am always looking for good coders to pitch in on mine. Thanks again, Anthony Ruffino [e-mail] 815-301-7606

[@derekbanas]

You definitely understand my way of thinking in these videos. I always thought it was better to avoid covering the details at times if it gets in the way of the topic at hand. I'm glad you see that because most people don't. I provide everything for free, so if you want to embed the videos, or use the code from my site in any way feel free to do that. I do all of this purely to help people in any way that I can.

[@jubinjuneja3135]

Its simple straight and clear. I have just listen only a few of them. I am in progress of listening more of deisgn principles session. Will recommend everyone who wants to learn design pattern... Thanks Derek

[@derekbanas]

Thank you for the kind message :)

[@derekbanas]

Sorry, but I haven't looked at BCEL for many years and I'm not aware of the background of this question. It sounds like a homework problem?

[@daywattly]

I spent days looking at different videos and examples of strategy design patterns that never explained or touched base with the instance variable of the interface. There was so many levels of confusion going on. Like how this abstract could extend multiple sub-classes of the interface being you can only extend one class. And why the need for the interface if I was just extending another class. This was the best explanation that I came across by far. Thank you.

[@derekbanas]

Thank you very much :) I'm happy the video learned up a complex topic

[@chiligarden]

This is the easiest tutorial about design pattern that I have viewed. I can't wait to finish viewing/learning from your tutorials.

[@derekbanas]

+chiligarden Great I'm happy that it helped :)

[@derekbanas]

It is in the works. It will come out immediately after the design patterns tutorial. Then I'll cover oop analysis and UML. The refactoring will follow that

[@zachhazlett3678]

Derek, Theses tutorials are life savers. I'm working for a company in a java boot camp accelerated program in which all of my classmates have previous programming exp. except me. To say I'm drowning in information overload would be a understatement. These tut's have helped immensely. God speed!

[@derekbanas]

Thank you very much :) i'm very happy to hear that they are helping.

[@derekbanas]

Yes that should work. You may want to give it a different descriptive name other than fly though

[@derekbanas]

Thank you very much :) I constantly do my best to improve them. I'm very happy that you enjoy them

[@derekbanas]

It should be an interface because it wouldn't make sense to have a Flys object. Does that make sense?

[@derekbanas]

Thank you :) Technically Fly should be an interface because in the real world Fly wouldn't be considered an object. I stick with that idea when writing code, but you may find a reason to use an abstract class that I haven't thought of.

[@jnryu661]

Hello, Derek, I am software developer having 3 years experience(Delphi/Oracle Pro*C, PHP(MVC)) and keep failing wtih interviews especially due to lack of understanding about OOP conception and design pattern. I just found your video and it does help me to understand those questions I have asked during interview and I think I will make it better next time. Thank you so much !

[@derekbanas]

I'm very happy that I could help :) I wish you all the best in your future interviews!

[@derekbanas]

I know I've simplified it and in doing so assumed that viewers would understand that there normally would be more than 2 choices. I do that because I'm planning to provide concrete examples in the future on when and how to use these patterns. I hope that makes sense

[@derekbanas]

Yes that is exactly it. Also if we can't think of something as a real object then it shouldn't be instantiated.

[@TigasFMS]

Got to thank you for these series. I failed my OOP subject last year (studying Computer Engineering) and this is being a great help. Studying while on my vacations. Thanks alot man.

[@derekbanas]

TigasFMS You're are very welcome :) I wish you all the best in your schooling.

[@derekbanas]

Thank you very much :) It is really amazing that techniques developed decades ago are still not used in many software companies?

[@MoRamzan]

I don't know enough to comment on C++/C#, but for PHP they are extremely useful. One of the major reasons that your tutorials are so good are that you obviously go to a lot of trouble thinking/preparing for them beforehand and they are presented very well - which means that the subjects/methodologies you are trying to explain are easily understood. Wish I'd come across your channel earlier!! Thanks again!! :-)

[@derekbanas]

Hi Assil, I'm not sure what you mean by website type? I try to use Wordpress if the site is simple. If not, I use a PHP framework the vast majority of the time. I lean towards Java and C / C++ application wise.

[@nitin.cherian]

Hi Derek. One of the best tutorials I have ever seen. I would like to point out the things I liked most about the tutorials. 1. Your voice. It just glues me to the tutorial. 2. The tutorial is short, crisp and awesome. 3. Even your comments and replies here is constructive and clear. 4. The code is well documented and very understandable. Thank you so much. Hats off!!

[@derekbanas]

Thank you :) I have a UML tutorial and I'm going to revisit these patterns again in my code refactoring tutorials that will start next week.

[@derekbanas]

Thank you very much :) I already have the UML tutorial finished. I hope you like it

[@derekbanas]

I should have explained myself better in the tutorial. I now realize that it can sometimes be confusing when I show multiple ways to do the same thing in a tutorial. I'm very happy that you enjoy the videos :)

[@derekbanas]

You're very welcome :) I did my best to make the gof book make more sense

[@derekbanas]

I included the classes that implement flys on the same page as I created the flys interface. You'll see it if you look over the code on my website. Sorry about the confusion. I normally don't do that in tutorials

[@nicolasap86]

I wanted to leave a quick note before I forget. Thank you so much Derek. Right now I'm in a Software Design class in which we have to learn these really tricky patterns. You do an absolute amazing job at explaining concepts(literally the best tutorials I've ever seen on the web for programming) I hope you continue to do this work and that you'll find a way to spin it into something even bigger than youtube videos(if you haven't already)

[@derekbanas]

nicolasap86 Thank you :) I'm very happy that I could help with patterns. Many more videos are coming and they will always be free.

[@tofupom]

If I am understanding this correctly, flyingType is an instance of the interface "Flys". ItFlys and CantFly are classes that implement this interface. How can we assign flyingType (an interface) to be a class? (ItFlys/cantFly)

[@TheRunner94]

These are by far the most helpful tutorials on KZbin for programmers. I am a first year computer science student and I have been spending hours in the library trying fully grasp structures of programs and object oriented programming. Great videos!

[@sambitkabi4617]

The tutorial is great.. Creating an instance of a Fly directly inside the constructor using new keyword leads to more coupling. Instead we can pass it as a parameter in the constructor to use polymorphism

[@smithlo4092]

Thanks Derek for such a great video. The first time I listen this video. I think I understand something. But when I try to watch it again. I feel I get lost. Here is my understand (which might incorrect) - Strategy Patterns can use when we have objects shared behavior and we want to avoid code duplication. - Instead of put that behavior as a attribute or method in SuperClass (which is bad because subclass have to override those method and this cause code duplication.) So, we use an interface. However using an interface does not mean just to move the method over there (which cause another problem -- each subclass will implement that interface and cause code dependent. (I do not sure I understand this point correctly or not.) So, Derek suggests that we use interface in a new approach: - Create an interface with behavior as a method. (Flys interface) - Then, create classes for each of those shared behavior and implemented method from behavior interface. (Itflys and Cantfly) - next, the SuperClass (Animal) have a new_field and use behavior interface as a data type - after that, the SuperClass (Animal) need to create a method to access to interface method. -- tryToFly() which return flyingType.fly() - and at object subclass construction -- Derek do interface polymorphically. -- flyingType = new CantFly(); // - at run-time, the instance of subclass (Dog) can access to behavior by using method in SuperClass -- trytoFly() which will call fly() method from the behavior class (Cantfly in this case) The benefit of Strategy Method is: a) I can add behavior which unaffected to Object SuperClass, b) As long as the method name in behavior implemented class not change, modification to the algorithm inside method won't cause any issue to the reference subclass. It would be grateful If someone could confirm my understanding or correct me what I misunderstand. Thank you.

[@derekbanas]

Thank you very much :) It is very nice to be able to help people understand this stuff. Many more videos are coming.

[@gypsicoder]

What if we use enum for the behaviour like Fly. In the enum initially we can put two values - 1) Can't Fly, 2) Can fly. And we can add new enum values whenever we want like 3) Can fly high, 4) Can fly very high. What do you think?

[@TheKillermob13]

i just love your speed...you did hard work cutting the video .. why we need to make class type to set if the animal are flaying or not , why not use premetiv type like string

[@VladimirTikhomirov]

Really nice video, thanks. Just few things. Why do you remove this @Override? All the IDEs add it when you want to implement a method from the interface and you remove it? Another thing is about this flyingType. I guess you can use the setter in the Dog class straight away and make your flyingType private field.