C++ Tutorial: Inheritance, Polymorphism, Virtual Functions, Abstract Base Class (Updated!)

In this video, I write a short program that utilizes the object-oriented programming principles of polymorphism and inheritance.
Included are examples of inheritance, polymorphism, virtual functions, abstract base classes, and a UML diagram for the example program.
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[@ladoctoradebug9788]

Pretty much everything you need to know about C++ classes. Thanks Prof!

[@ProfessorHankStalica]

Hi, Linda. Really happy to hear that you enjoyed the video and got some use out of it! Thank you so much for the super thanks and that will go into the upgrades fund for improving the channel and videos for you guys and the students. Thank you very, very much.

[@liboyan7010]

The best OOP application tutorial in C++ I ever watched!!!!

[@ProfessorHankStalica]

Thank you for the kind words and comment.

[@bern1223]

This is how computer science SHOULD be taught! My school just used powerpoint and we never ever coded in class so I would never know how to actually implement these concepts. Thank you for your help!

[@BidoofGames]

yee

[@ProfessorHankStalica]

Glad you found it useful!

[@petlover9580]

@@BidoofGames in g ty TG and a TV g ggg gg h gf gf is ggg good ty tvg

[@mihirpatel3010]

Thank you sir. You're one of the best when learning C++ 🙏

[@ProfessorHankStalica]

Thank you for the kind words and I'm really happy you getting value from the videos.

[@jhc641]

This about 30 minutes video was way crystal clear than my 2-hour CS lecture. Thank you for your quality video.

[@ProfessorHankStalica]

You're very welcome!

[@johnpaulrosario5538]

The best OOP application tutorial in C++ I ever watched. Simple and easy to understand explanation.

[@ProfessorHankStalica]

Wow, thanks!

[@alexandruteodor3585]

Thank you! I'm finally starting to understand what is polymorphism used for.

[@nikopapiashvili1627]

this was better than 4 hours of lecture, thak you very much.

[@ProfessorHankStalica]

Glad you liked it and thanks for the comment!

[@nolans7997]

Amazing video, thanks for all the help. Needs more teachers like this

[@ProfessorHankStalica]

Glad you found it helpful and thanks for the comment and support.

[@maxwen6447]

I was struggling to create a vector of derived classes and for some reason it's difficult to find good examples but this explanation was outstanding. I'm going to watch all your C++ videos now because of your excellent teaching style. Thank you for this resource.

[@shaheerhasan4568]

Thank you professor hank this helped me a lot I struggled all through cs 115 and finally I understand how inheritance and polymorphism works. and this got you a new sub!!!

[@ProfessorHankStalica]

Glad it helped!

[@Spectrej10]

Thank you so much for making this! I've been feeling some disconnect between the content of my CS class and my understanding and seeing this helped me understand what we've been talking about so much more.

[@ProfessorHankStalica]

Glad it was helpful!

[@jesusgarciagutierrez7301]

The best video on the internet I have ever seen about inheritance, thank you so much!!!

[@ProfessorHankStalica]

Wow, thank you!

[@truthspeaks651]

Excellent tutorial. You nailed it. Thank you very much, this was a well designed and well presented video, only someone insane could give it a thumbs down. I can't wait for more tutorials from you. Keep up the good work.

[@ProfessorHankStalica]

Glad you liked it!

[@gepic8329]

Very nice and simple way to explain an actually very complicated topic! That was exactly what I needed for my current project! Thank you!

[@ProfessorHankStalica]

Glad you found it useful!

[@chakt2772]

This is an awesome video explaining difficult to understand C++ OOP concept in a simple and straightforward way. Very well thought of samples from inheritance to virtual function and to polymorphism. Sincere Thank You!

[@ProfessorHankStalica]

Glad it was helpful!

[@shankarghimire4492]

Wow! Very well and clear explanation and demonstration! Great Job Hank! :)

[@ProfessorHankStalica]

Glad you found it helpful and thanks for the comment and support.

[@zengceng]

was lovely to listen to this while doing my stressful assignment

[@ProfessorHankStalica]

*whispers* glad you like it....

[@kidbuu1328]

This is so well paced and explained. Thank you very much for your effort professor!

[@ProfessorHankStalica]

Glad it was helpful!

[@extensivemoney6797]

This be so dope Professor Hank!

[@omarmohamed3473]

Fantastic lecture!

[@donovanhodges5713]

Thank you for the video. I enjoy your explanation and method of explaining concepts.

[@ProfessorHankStalica]

Glad it was helpful!

[@mahdishirazi5785]

thanks very much. it is really worth a thumbs up professor Stallica, very very excellent video with great example to demonstrate the concepts, although it would have been better to inherit two abstract classes from the Shape class, being named TwoDShape and ThreeDShape, then assigning a virtual function getVolume to the ThreeDShape class and then inheriting the Circle and Rectangle classes from TwoDShape and Solid class from ThreeDShape; so that the getVolume method will do whatever the getArea method did for Solid in your code (returning length times width times depth). the getArea method you defined, is later used in Solid class but it doesn't return the area, it returns the volume, and that is not wrong in a way to generate errors, but is kind of weird for a getArea method to return the volume and not the area itself.

[@ProfessorHankStalica]

Thanks for pointing that out! Will have to adjust that in a future remake of this video!

[@robcambr]

thanks for the lesson professor!

[@ProfessorHankStalica]

Glad you liked it. I do have an updated version of this video if you'd like to see that as well. Good luck with your studies!

[@Diamond_Hanz]

Thanks prof hanky!

[@ProfessorHankStalica]

You bet!

[@saif5151]

thank you

[@ProfessorHankStalica]

You're welcome!

[@cerealnomilk9657]

thank you !

[@ProfessorHankStalica]

You're welcome!

[@rfdave3980]

Thank Prof Hank. Great explanation.

[@ProfessorHankStalica]

Glad it was helpful!

[@garyvillar8992]

Great video! Quick question do the objects need to be dynamically allocated in order for the dynamic binding to work?

[@ProfessorHankStalica]

It does require pointers.

[@animalzblc8960]

18:00

[@maxim25o2]

You forget to mention that when You are deleting objects in vector, or another storage, vector also must be emptied. Like " shapes.clear() ", otherwise in side of code, when vector is working in loop, and it will be overridden, then program will crash, because, the old appended objects as pointers are not existing anymore, and it will point to garbage. After deleting objects, always remember to clean vector. I have that situation, when vetor was holding pointers to non existing objects.

[@ProfessorHankStalica]

That is absolutely correct, however, since the program was terminating immediately after deleting the objects, it doesn't really matter. As a matter of best practice though, if I had more code following the for loop deleting objects, you are 100% right I should have cleared the vector.

[@mandeepkhadka388]

Thank you, this was both very clear and concise, I just have one question though, what's the exact purpose of using the 'const' keyword after almost every method name? ( e.g. double getRadius() const { return radius; } ) I have not used 'const' this way with function names and everything seems to work fine without using it as well. Thank you in advance.

[@ProfessorHankStalica]

It is a way to explicitly mark the method as an accessor and prevents any statements within the method from changing the contents of any of the class attributes. For example, class Foo { int x; public: void bar() const { x = 5; } }; Will not compile.

[@mandeepkhadka388]

@@ProfessorHankStalica thank you once again :) for the comprehensive reply.

[@imrank340]

Please increase MS code dev studio Font size much appreciated. Thanks for explaining "dynamic Bindings".

[@ProfessorHankStalica]

I hear you and thanks for the comment. This is a really old video and in recent releases I did make that adjustment. Here is updated versions of this content: kzbin.info/aero/PLaatXkJEXKyKlx6H44MbV2d63AmudD5sd

[@marcinlesniewski4571]

27:18 Line 55 Can we use Ractangle::getArea() instead of getLength() * getWidth() ? , except that this is the formula for Volume, not Area;) Should be 2 * Ractangle::getArea()+2*getLength()*depth+2*getWidth*depth

[@ProfessorHankStalica]

Thanks!

[@thanasiskotsompolis7821]

You create a vector of Shape pointers, but each pointer points to something with more memmory than it should have(Circle,Rectangle,Solid) . How is that allowed??

[@ProfessorHankStalica]

Because pointers aren't objects.

[@PickleADC]

pointer is just a variable that contain address of another variable/object so yeah it's not related to the object itself

[@TpojkaVEVO]

solid.getArea() { return 2 * ((length * widht) + (length * depth) + (widht * depth)); };

[@maxim25o2]

You don't need use constructor in Circle, I was playing with similar code and I found out that calling to fincion in Shape I was able also to achive this same. using namespace std; class SHAPE{ protected: double height; double width; public: void s(double length){ height = length; width = length; } void s(double h, double w){ height = h; width = w; } virtual double area(){ return height * width; } }; class CIRCLE : public SHAPE{ public: void c(double w) { s(w); //************ this is call to function I didn't use constructor at all. } double area(){ return 3.14159 * pow((width / 2), 2); } }; //******************** void showarea(SHAPE& shape){ cout

[@patrickorone1149]

Great bro

[@lesstor99]

if you don't use a constructor at all, the compiler writes one for you, remember this: RAII (resource acquisition is initialization) Initializing the member variables is not all the constructor is doing... Also, you might want to think about design choices...in a way, classes and objects are supposed to mimic real world "objects"...likewise for inheritance...its supposed to make sense

[@ProfessorHankStalica]

Great answer here. This person object-oriented programs.

[@maxim25o2]

@@lesstor99 I know what You mean. Creating obiect in side of another obiect. But this code will create obiect by inheritance anyway. I don't see sense to play manually with constructors. Because it will create that class always. But there is a reason why sometimes can be used constructor and destructor. If Your class must live longer then Your parent or outside of function where was created. Or You use if statement to create obiect only if there is a reason, like with low memory embedded systems. Or if Your obiect need live shorter time in side of function because You have big loop statement.

[@brandonarnold7430]

You can't tell me that dislike isn't himself. Who but the creator would dislike this video :/

[@ProfessorHankStalica]

Thanks for the compliment...I think? Took me a sec to understand what you were saying...I guess? LOL. Glad it was helpful!

[@ivans7]

i don't wunderstand why ppl think making things complicated is cool !! That's really unwelcoming !! I mean inheritance could be taught with simple variables and a single function...You genius make things tough and there indians took the advantages😑😑

[@ProfessorHankStalica]

I don't understand it either. Maybe some people think it makes them look smarter than they are or something? Any fool can make something overly complicated. It takes genius to make something simple. I'm not saying that I'm a genius or that I'm better than anyone else, just that it's my goal and philosophy to make things as simple as possible. Sometimes, I do a great job. Sometimes I have to try a few times to get it right. Teaching takes practice just like learning takes practice.

[@ivans7]

@@ProfessorHankStalica It'd be better if you can use simple terms in your videos

[@ProfessorHankStalica]

Thanks for the feedback and I can understand that. I try to keep it as simple as I can, but there are some terms you just can't simplify. An object is an object, for example. There are terms that my students are expected to learn and use so that's usually why you'll hear the jargon that you do.

[@temercastle7193]

16:15 starts talking about Virtual Functions

[@melmthombeni9761]

Its not that much visible otherwise thanks