The Only Time You Should Use Polymorphism

The only time you should use subtype polymorphism is when you have behavioural variation in the subtypes. I teach two university courses on object oriented programming and I see this problem a lot. Let me explain. RECOMMENDED READING:
🛠️ geni.us/k8KhT3 (Refactoring)
⭐️ geni.us/zzlx (Dependency Injection: Principles, Practices, and Patterns)
💎 geni.us/hNDE (Elegant Objects)
🏛️ geni.us/IBhtLnh (Clean Architecture)
🧩 geni.us/nlbA6 (Head First: Design Patterns)
Read my FREE book on Object Oriented Programming:
🚀 theobjectorientedway.com
Watch next:
• Always Use Interfaces
CONTENTS:
00:00 Thesis
01:16 Example 1
03:28 Example 2
06:25 Example 3
13:26 Summary

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Finally he remembered his password

[@ChristopherOkhravi]

🤣🤣

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called it!! 😂

[@himanshuyadav6672]

Where you were?, will you make video contunue now​@@ChristopherOkhravi

[@madyogi6164]

This must have been some variation in data.

[@Adam-326]

He randomly came back after three years! Tak! Good to see you again.

[@rafael.aloizio1769]

Yessssss I'm glad he is back man, I've learned so many things important on my career because of his videos

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Love him, jest super

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OMG I can't believe this, I asked him last week on Twitter when he is coming back..and here he is. 🐐

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What are the chances he’ll stay with us for some time now 😅

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@@DerRabeKirilldepends if project manager leaves him alone

[@Pawemie]

I like to think, that you got so annoyed by someone at work using subtype polymorphism the wrong way, that it brought you back here ;)

[@ChristopherOkhravi]

I teach at a university so I read a lot of student code 😉

[@tony2351992]

in which university do you teach I need to attend there, you're a CS legend @@ChristopherOkhravi

[@BANANAS2011]

I wish more people in your team do things in wrong way that you make more videos to teach others 😂

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literally just watched your design patten playlist, thinking why hasn't he posted for 3 years. perfect timing

[@williamcory4689]

Welcome back! Got a huge amount of value out of this channel in my early days of becoming a dev

[@andreaskonomis3]

Have been watching your Design Patterns series and the code walks videos and was always thinking if I ever wanted to have a youtube channel it would have been of this style. If only he was back. Wish granted, welcome back, so happy to see notifications from you! :DDDD

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Awesome to see you back Chris! I’ve learned a lot from your videos, and have always enjoyed hearing your perspective on things. 😎👍

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Best notification from KZbin in ages. I hope you've got more for us. 100% my favourite videos covering software development!

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I've never been more engaged with software engineering KZbin content. Your presentation skills are excellent.

[@maurobastasini8704]

Great to see you again Christopher. Miss your videos of design patterns and discussions about principles. Welcome Back!!

[@Michaeljamieson10]

please continue have been rewatching your old stuff so glad to see this

[@KlamerR69]

Welcome baaaaack!!!!!!!!! Happy to see you around after so much time! Hope you'll stay for a while, your content and way of explaining things are precious.

[@barisaxo]

I've been watching your playlists whilst working on my project over the last year, and this video is so relevant to what I'm currently working on, and exactly what I've been asking myself while working on my current systems. Being self taught I don't know the theory very well, so I would had never known that I was dealing with 'sub-type polymorphism'. Good to know I've been going down the right path, and also to know what it's called!

[@dhruvachandra8210]

Suddenly you appeared out of thin air, please be consistent. Love your content.

[@maximus1172]

No one told you to wait

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we aint entitled to his time

[@bakaoug4g491]

He can post whenever he feels like posting. How entitled are you. Anyway thanks for the content ignore comment like above

[@Ruzi1996]

I started watching him on thursday, fell in love in his way of teaching, and was thrilled when saw that last video was posted 3 years ago. And now he appears out of nowhere 😂 If you were giving lectures on my Uni, i wouldnt miss a single one

[@rizwanfirdous]

Last month i was discussing with my friend about Design patterns and in that discussion i recommended him your channel. While discussing i said to him that don't know why you aren't posting any content. I was little bit worried about you. Now i am very glad to see you back. 🥳🥳🎉🎉❤❤❤

[@nullset11]

Glad to see you're back uploading videos! Your series on design patterns were instrumental in taking another step in my career!

[@muhammadhamzashujaat6767]

Love to see you again, I look forward to rewatching as much of your videos as possible !

[@eladfeldman1152]

happy to see you are back! keep the content coming! learning a lot.| love the whiteboard, the editing and the why you teach :)

[@r1konTheAutomator]

WHOA! i started watching your pattern videos like a week ago, binging them while at the gym, while taking walks, etc. i was like "eh it's been a long time since hes posted...he was a good teacher" and then here you are!!

[@artemisSystem]

Whoa, seeing you in my sub box is not something i expected today. Long time viewer of the channel, since the ramda days! Good to see you back. Your channel helped me get into functional programming, and now i'm absolutely obsessed. Do you have any plans for more FP related videos?

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I came to the comments section to share my excitement about your return. But, wow, I didn't expect there to be so many of us!

[@SudhakarChintapalli]

Hey @Chris, it's great to see you after such a long time! I've always been a fan of the way you present content with crisp editing.

[@RyanCortino]

Man, I was so happy to see your face in my feed again. Glad to have you back, your videos always helped me understand these concepts so much better.

[@alexstone691]

I did not expect you coming back, loved your design patterns, glad to see you're doing well!

[@rickydownload]

From last week I started watching your Design Pattern playlist and thinking why Chris stopped posting videos for last 3 years. To my surprise there was a notification😮. Your teaching is so great and natural, not everyone gets so easily. Keep up the Great work!

[@liquidpebbles]

Glad KZbin was smart enough to recommend your video. Glad to see you posting. Always top notch stuff.

[@davidntumba2447]

I didnt even fully read the title, I just saw the thumbnail and clicked. Welcome back good sir.

[@RajivKumar-qj9nw]

So happy to see you back. You're the sole educator whose KZbin videos I choose to view at regular speed, even when they extend to an hour.

[@chirayumishra1185]

Welcome back Christopher. Good to see you back 😊 Keep up the good work and make learning fun and easy. All power and good wishes ❤

[@ripanpramanick425]

Your Design pattern playlist is the best I have ever seen on any channel/courses. It was about a year ago I started and completed the DP videos, but was disappointed to see no more , and randomly today this video pops up on my feed, very happy to see you again hopefully you will complete the rest of the patterns too 😊. I tried connecting you on LinkedIn too but it was restricted I think 😅.

[@benjones1452]

Welcome back, I have missed your content, it is great. Your analysis has been vital to my programming evolution, if only I'd have had teachers with your energy.

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Finally you are back! I enjoyed so much your design patterns playlist.

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I watch your videos and you are the first teacher whoes course i can buy without thinking about money.

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Legend is backkk!!! Good to see you, your system design videos are epic!! MASSIVE THANKS

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I don't have words to describe how happy I am to see you back.. Love your style of teaching

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Welcome back Chris. Have learnt a lot from your design pattern series!

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Thanks for your work, I got a masters in software engineering 2 years ago and your videos on the design patterns really helped me.

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Happy to see you upload after 3 years love the way you teach..

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Your teaching is the greatest and simpler....❤

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I missed your tutorials man, good to have you back!

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Welcome back! Your videos helped me a ton while getting my degree - good to see you're still at it!

[@ChandraShekhar-by3cd]

Welcome back! Please upload more videos on system design and LLD. We appreciate your effort!

[@drewbruggman]

I didn't learn anything, but the way you described the information in the video *clarified* what I'd already known -if that makes sense. You are excellent at explaining things in very clear terms, and I appreciate that. Subbed.

[@ChristopherOkhravi]

I'm very happy to hear that. Also, thank you for the sub. Welcome 😊

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I like this format. My ADD was trying its best to block the info, but this guy just kept going :)

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Oh hey look who's back! Thanks for the video! Ur gof patterns videos helped me a ton a few years back

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I missed your videos, thanks for coming back!

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Oh my god. I used to watch your videos when I started learning programming in 2021. Right now, I have an interview with Google scheduled next week. You don't know how happy I am to see you back. Thanks for coming and welcome back :)

[@ChristopherOkhravi]

Glad to hear 😊 Best of luck on your interview!

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Welcome back! So excited to see you back! huge fan of your videos. Thank you!

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It's so good to have you back. Thank you 😊

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Good to see you after 3 years. I love the way you teach.

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Thanks for all of these and welcome back!

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I didn't realise you hadn't posted for three years! I've been taking a break from coding but had to watch this video! Please keep posting!

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omg great to see u again! Ur videos has helped me tremendously during my time at chalmers, and im actually now TEACHING the same course i used ur videos to pass years before! Will recommend ur channel to all my students!

[@ChristopherOkhravi]

Thank you 🙏😊 And congratulations

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you did really well with this video, i was able to flip into it and out of it, while just listening and you never lost me. i now know what you put into this video and thats always nice!

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[@ChristopherOkhravi]

I'm very happy to hear. Welcome 😊

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it's been a very long time, nice to see again man!!

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I've really missed these talks. Welcome back!

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Kul att se att du är tillbaka igen! Dina förklaringar av designmönster hjälpte mig enormt under skoltiden. 👍 Man önskade att fler lärare var såhär pedagogiska.

[@ChristopherOkhravi]

Tack så mycket!

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Welcome back! Good to watch your video again!

[@nonickname1231]

Previously, thank you for the knowledge, and welcome back. What I get from the explanation is: We should/must prefer to be implicit about a specific type of data that has the same structure and behavior, instead of being explicit (where we define it based on the actual concept or domain) about that type (CMIW).

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Love to see you back, hope all good at your end. You have unique way of communicating complex things, Keep making video.

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The man, the legend, welcome back

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Welcome Back, Great to see you after 3 years :D

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Hej, you are back. I have mist your videos, they have helped me so very much. Thank you for another interesting and great video.

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Welcome back, sir. Happy to know you are still creating content.

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I was waiting for this quality content again, thank you so much !!!!

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I just remebered your design patterns series from years ago and was looking what you were up to. Great timing.

[@ChristopherOkhravi]

😊😊

[@ChristopherOkhravi]

Thanks for checking in again 😊

[@iulianbojinca7309]

Welcome back! Thank you for this! The cliffhanger in the end...oh man, please don't let us hanging for too long

[@ChristopherOkhravi]

Gotta leave some loops open 😊😊

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I'm extremely happy you are back. Thank you.

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bro scared me with that jump in the frame haha welcome back! Thanks for the Design Patterns series which helped me a lot!

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Your teaching is simpler and also in depth, good to see you back on youtube. Please create more good quality content !!

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Loved this video. Thank you so much for the bite-size CS training. Love your style, heart, and expertise.

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Damn you're back! Thank you very much for the content!

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You're a fantastic teacher. Welcome back !!!

[@TazG2000]

I would add a point that "variations in behavior" can also come from _outside_ the class - a class can just be a data type, without being responsible for all the ways the data will be used. Imagine an Attack subtype, EnergyAttack, which has an additional property EnergyType. Now Scratch is a base Attack instance, and Thunderbolt is an EnergyAttack (with EnergyType = Lightning). Looking at just the class definitions, you could say this is a data-only variation, but it makes sense because the change is in the data structure (an additional property), not just values. These subclasses may or may not implement variations in behavior themselves, but _allow for_ external variations by being different types: We may have many general functions that work with the Attack type, as well as some functions that accept EnergyAttack specifically and work with the EnergyType property.

[@alinapostol2230]

We've been waiting for you to come back! - so WELCOME BACK ^^!

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Word to mother....ur design patterns videos helped me nail an interview in 2017 🤣🤣🤣. Now I'm a Lead software engineer. Thanks

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Once again, you enlightened me about something that might seen implicitly known and simple but in reality a truly good software engineer needs to be absolute aware of.

[@siddharthkothari007]

Welcome back Chris. loved this one.🙏

[@ReneSteenNielsen]

WB Christopher, --- I have a very curious question: 6:55: YES, why? 7:35: You MUST have had a way simpler example at first, where you still used "IAttack"; which is sort of revealed by you forgetting to delete "Stun". I personally believe that you might have overthought the lesson a bit here. Despite how rational you try to justify the new super type and broader scope. As I see it, you could easily still have stuck to: "IAttack". The third example would then showcase e.g. "Attack" and "Stun". The latter could implement e.g. a timer for the duration of the stun. That would now also be accounted for as an introduction of a new behavior and the whole thing would be fairly straight forward to understand, at least in my book 🙂 Instead, I feel like, with the current approach (creating a broader super type) students could then easily start wondering - when is enough - enough? You could then arguably keep pushing the goalpost, higher and higher in responsibility, instead of keeping the example grounded where it all began... I guess this also leaves the solution vulnerable to potential constant refactor, just as the slightest requirements change regarding the architecture... I think you somewhat try to clarify for this yourself around 9:55... Maybe I'm just too caught up in the semantics or too curious... Let me know, if I misunderstood something very vital 🙂 --- Thanks!

[@oleksandr.pastukhov]

Good to see you again! Welcome back!

[@Jeff-xh4sy]

I used your design pattern videos to pass my cs class last term and here you are again lol

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So nice to see you came back,thanks

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Your knowledge is actually so precious. I love the fact that you just use concepts with whiteboard. Thank You for coming back to us, You can make a lot of us promote with your videos!

[@ChristopherOkhravi]

Thank you very much for sharing 😊😊

[@observable-compositions-1996]

Thanks for coming back man

[@rudreshgp]

Thank you Christopher for your design pattern series. That is one of the reason I got promoted 🙏🙏🙏

[@ChristopherOkhravi]

Congratulations! 🎊😊

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Welcome back! Good to see you!

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We miss your valuable teach.

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This is one of the most engaging software videos I've ever seen

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I am in love with this guy !!! He radiaties positivity and passion :) Glad to see u again Christopher:)