Understanding The Visitor Design Pattern

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Understanding The Visitor Design Pattern

Рет қаралды 57,677

Ryan Schachte

Күн бұрын

Пікірлер: 164

@TheSimpleEngineer 5 жыл бұрын

Let me know what design patterns you want to learn!

@TheSimpleEngineer 5 жыл бұрын

@@dg10mcdos cool 🙂 I'll do that one next

@hinathahseen8643 5 жыл бұрын

Thanks for the above one. Double dispatch couldn't be simplified more.Can you t explain examples of Extension object and Template method design pattern:)

@mirazzaidi 5 жыл бұрын

Can you do a decorator?

@deepankarsingh7230 5 жыл бұрын

Can you please make a video on strategy design pattern?

@Nemecis313 4 жыл бұрын

I would like to understand the Mediator design pattern if possible. Thank you for this video!!

@mehmeterdem7581 5 жыл бұрын

This is probably the best video on the net for this pattern with a perfect example.Thank you!

@ruixue6955 3 жыл бұрын

2:50 UML dia of Visitor Pattern 4:20 the original piece of hierarchy 6:50 why - single vs double dispatch 7:39 single dispatch 8:14 what single dispatch allows us to do 9:58 double dispatch: interaction of 2 objects 10:12 example 10:28 modify the interface: in Animal interface, add makeSound(Dog) and makeSound(Cat) 11:45 *compile error* due to not support on double dispatch

@rahulsaxena9103 3 жыл бұрын

He has made the pattern as easy to understand as hard it is going through other explanations on the web. Amazing!!

@dhapategeetanjali741 4 жыл бұрын

I wonder all over the internet to find the best to learn visitor design pattern and finally landed here and writing comments middle of the video, This is an awesome video so far I came across. Buddy keep it up you are the best.. !!!!

@ashrasmun1 5 жыл бұрын

I would love to see constructive criticism from someone who disliked this video. I think it's unbelievably helpful, especially given that you explained the whole "dispatch" thing, which is not obvious at all for beginners. Thank you very much!

@TheSimpleEngineer 5 жыл бұрын

Thanks, glad you liked it!

@genovo 3 жыл бұрын

Problem: 12:56 Solution: 28:00 Fantastic video!

@chiranjeevisaride8655 3 жыл бұрын

The best explanation anyone can find on this planet. Absolutely loved it!!

@PrashantGangwar Жыл бұрын

I've seen lot of videos on this pattern but this is most real life understanding video on Visitor pattern, Thanks for this amazing video... luckily found this

@reallylordofnothing Жыл бұрын

really good video. came here to understand rsql-parser visitor pattern. I can see that this pattern explains open closed principle very well

@aelafdev 3 жыл бұрын

by far much cleaner explanation. visitor is mystrio no more. thank you

@zizimouad8291 2 жыл бұрын

THE only video explain this pattern in the right way ! explination, diagramme and exemple with code all are perfect

@michaeljuergen4326 3 жыл бұрын

Very good explenation, this is the Video I was searching for the whole time

@MrEthera 4 жыл бұрын

This was amazing! A colleague of mine used this pattern without using "visitor" in the name. I understood the structure and how to use his design, but I didn't fully grasp everything that was going on or how he even came up with it. He mentioned visitor and here I am. Thanks for the concise but real world example.

@TheSimpleEngineer 4 жыл бұрын

Great to hear!

@usamakhawaja8571 5 жыл бұрын

Just half way through the video, and I would like to say "Good Job". (y)

@deltaphilip8611 3 жыл бұрын

Finally make sense. Knowing what to accomplish makes it easier to understand how to do it

@AlbertoGS1990 5 жыл бұрын

You are the best explaining design patterns. You should make a single video for every single pattern in the book. Thanks a lot for your teach.

@burakkirazli3759 3 жыл бұрын

This is the most clear explanation I have ever seen.

@piotrpieniak738 5 жыл бұрын

I'm so grateful for it, good job! I always struggle with theoretical explanations and definitions, so combining them with actual examples made it so much easier to understand.

@andres5709 2 жыл бұрын

i'm no kidding there's a job offer in play here, and I have to deliver a code using this very pattern and i couldn't get it before watching this amazing explanation of yours! thank you for time and help from Brazil!

@soumenadhikary4332 3 жыл бұрын

This is one of the best explanations of double dispatch I have come across!

@amitsamratmaurya3170 3 жыл бұрын

Best content so far!! You won't need to read anything else after watching this.

@kinvain 3 жыл бұрын

Really like your video. Especially that you extend fake Animal interface use case to something more realistic.

@adamblance3346 2 жыл бұрын

Thank you! So many other videos on this feel rushed and don't go into enough detail.

@FernandoNavarro_1 3 жыл бұрын

Very clear presentation and illustrative code. Thanks

@ArvindDevaraj1 4 жыл бұрын

very clear explanation of visitor pattern with real world examples

@ilstam9942 5 жыл бұрын

Awesome explanation and helpful example! I hadn't realize before about the double dispatch problem. I really liked that you didn't over-explain things keeping it short and to the point. Also thumbs up for cutting out the tedious parts where you just paste code. Thank you!

@glenndify1 3 жыл бұрын

One of the best explanation of the visitor pattern

@williamquintero3133 3 жыл бұрын

Excelent bro... i've just spend a lot of time trying to understand this patterm. And you did it in just 30min :) thanks..

@saurabhchaturvedi6982 3 жыл бұрын

Awesommest post on the internet on Visitor Design Pattern !! Understood everything in such a simple way that its gonna stuck in my mind forever !! Subscribed !! Thank you..may you have many more "Visitors" on your channel 😅🤟!

@deepankarsingh7230 5 жыл бұрын

Amazing explanation. I like discussions a lot when it cover the background as well like why something is needed, current limitations in some paradigm and ways to solve that. Thanks a lot for the video. :)

@bimarshsharma7556 3 жыл бұрын

Thanks for the clear and straightforward explanation.

@sohailiftikhar207 4 жыл бұрын

Beautifully explained.

@speyck 2 жыл бұрын

Gotta be the best explanation of the pattern I've seen yet. Thank you for making this free :)

@fakhrshaheen3394 5 жыл бұрын

very well explained.it's really one of the most underrated patterns

@samitabbakh8409 2 жыл бұрын

Really nice explanation. I hope you would do a complete playlist of all design patterns. It is a shame that you made only 3 design patterns.

@yolokazinogantsho8111 3 жыл бұрын

Great great great explanation. Totally understood! Big thanks

@kankipatisaikumar 3 жыл бұрын

@the simple engineer Great explanation, easy to memorize

@MN7Editz 3 жыл бұрын

Very good explanation. So far the best explanation and presentation on this pattern and finally I got it understood. Thank you very much.

@whatever6223 2 жыл бұрын

Excellent explanation. Thank you very much!

@ambarishkapil8004 3 жыл бұрын

This was very nicely explained. Thanks

@lucykuo4769 4 жыл бұрын

Finally found a great video for visitor pattern! Hope you can make more design pattern tutorials

@andrewprotasenya7469 3 жыл бұрын

thank you very much, I finally understood the essence of this pattern

@TheFrogfather1 Жыл бұрын

Nice clear explanation. Thank you!

@nikolaradovanovic4883 3 жыл бұрын

Great content. Much cleaner than many of docs I read.

@YakimRachev 4 жыл бұрын

The greatest tutorial for the Visitor pattern I found so far! Thanks.

@Rastrigin 2 жыл бұрын

great job man, love your setup as well

@rolandsoftwareguy2515 2 жыл бұрын

Excellent explanation especially of the why. A lot of tutorials just go straight into the how. I think given the extensibility problem, I might have initially gone down the passing of delegate route or maybe another interface - but I guess this seems somewhat tidier. Note to any other C# Developers reading before watching, the video is still easy to follow. Well Done 👍🏾

@herrgrillparzer 3 жыл бұрын

Such a clear explanation and great examples. Thank you so much for this 😊

@HassanBadir 4 жыл бұрын

damn, this is well explained, when I look for a new topic to study I usually run through multiple videos until I understand it completely, this time i watched the whole video once and got it on first time this was amazing thanks a lot man, big like!

@MirekKrenc 2 жыл бұрын

Very well explained. Thanks!

@TommyBoy7Heads 2 жыл бұрын

Legend.. thanks for the great explanation man.

@atulsaxena4286 4 жыл бұрын

Very nice videos probably the best on the internet. Please do other patterns as well with the same kind of explanations you have done in these videos. Thanks.

@gunjanchaudhary9716 2 жыл бұрын

The best Explanation !

@tobechukwunwatu848 3 жыл бұрын

Concise!, Clear!! and Simple!!! Thank You!

@MrJonnis13 3 жыл бұрын

Simply excellent explanation of this design pattern. As you said, this one is underestimated but it is super useful. Please consider doing some other design patterns, especially the "not easy" ones Thanks again for this video

@drewenia 4 жыл бұрын

The best video on the internet. Thanks for.

@jaydenhooper 2 жыл бұрын

Excellent explanation!

@illosophycom 5 жыл бұрын

Isn't this still tightly coupled though? If you get rid of the Bronze Card or add a Platinum card, you have to update your OfferVisitor interface and all of the classes that implement OfferVisitor right? That's still a maintenance nightmare. It seems like the problem wasn't solved but just relocated.

@TheSimpleEngineer 5 жыл бұрын

There will always be some coupling, but the amount is reduced as your class base grows large.

@prateeksingh4078 5 жыл бұрын

loved the way you explained it with an implementation made the video so much more intuitive!!

@deepakkeswani3241 4 жыл бұрын

Super explanation of Visitor Design pattern.

@samilozcelik8356 4 жыл бұрын

Thank you. Perfect explanation with a perfect example.

@AB-os3jy 3 жыл бұрын

it would be a hit if you could do a series or video that puts together and deploys a multi platform mobile app. bonus if it has animation , audio and 3d capability.

@nadiadima9449 3 жыл бұрын

Very clearly and neatly done. Thank you!

@Kavorka666 4 жыл бұрын

this is great video. I wish you would continue more on this playlist.

@simoncatteau2879 3 жыл бұрын

Very clear video!

@peacefulwater9689 3 жыл бұрын

very good video, explaining single vs double dispatch really cleared it up. The only thing I didn't like was the intro

@luyandamsomi8402 2 жыл бұрын

great job man, really appreciated💪👏

@cursedkid25 5 жыл бұрын

I genuinely loved your video and your explanation

@256sks 3 жыл бұрын

Thank you for good explanation. Your final implementation require small correction. Visitors classes should have overloaded method rather than different name for different CreditCard. Otherwise it will work without double dispatch.

@mrowox 9 ай бұрын

This is really fantastic. Is it possible to combine this pattern with the Factory pattern for example to dynamically determing which credit card to use in a certain scenario

@allen0hu 3 жыл бұрын

WTF this is so well explained! Thanks, saved my finals :)

@rezasaidafkan8698 3 жыл бұрын

Crisp! Good job!

@csforlyfe4206 4 жыл бұрын

Very good explanation of the concept! Helped a lot!

@ArchaeanDragon 9 ай бұрын

GoldCreditCard silver Had no effect on the running code, but boy did it trip my OCD! lulz :P I think it would have done better to drill into why you couldn't pass cat to itself. Basically, you can't pass ancestors references into descendant params and vars. The compiler gives you that hairy eyeball because the running app can't use a crystal ball to figure out which descendant you meant. I think it was part of your higher-level explanation, but for newbs, the underlying problem wasn't as clear.

@agatalach2855 4 жыл бұрын

This is a great video. Super clear explanation, great example, and the whole video was really well done. Thanks so much for your work, it's really helped me understand the pattern and I am now going to go check out your channel for more content, which I'm sure will be as good :) thumbs up!

@LemmeTellMe 5 жыл бұрын

Good job on the video, heads up though the intro music could be tuned down a bit since it feels a lot louder than the rest of the audio

@saeedmirzaei1 4 жыл бұрын

Excellent explanation. Thanks so much.

@andreslipinski5922 4 жыл бұрын

Thank you for doing this. Really clear explanation.

@SylvainBrunerie 3 жыл бұрын

Great explanation, thanks! My question is the following: we made CreditCard easy to extend without needing to modify it, but now OfferVisitor kinda is in the situation we wanted to avoid, right? If we create a new PlatinumCreditCard, the OfferVisitor will have to define visitPlatinumCreditCard, and all the visitors will have to implement it. It feels like we need to take a guess at which side (credit card or offer) is more likely to be extended in the future, and use a visitor pattern for that one. But we can’t have that for both of them. Is that right?

@rolandsoftwareguy2515 2 жыл бұрын

I think the idea is you might add a card once or twice a year but maybe 3 or 4 offers a month. I guess what we would normally to is have a GetCashBack(CreditCard, Offer) method but then there would be the overhead of maintaining a datastore

@GiorGoS07031992 2 жыл бұрын

I think so like the a scenario like the one described on this video. You don't come up with new credits cards every day, but you may get new offers every day/month.

@karanagarwal3091 5 жыл бұрын

Beautifully explained

@mireazma 3 жыл бұрын

The way I see it visitor pattern doesn't make you write any less code but it gives the advantage of decoupling. But even so, it kind of does and then it doesn't. In the "multi-dimensional" case like cards/offers it all depends on which of the dimensions you're likely to have more classes added. Even if card types are issued occasionally, for every new card you have to make modifications in every _offerVisitor_ . And there may be an order of magnitude more _offerVisitor_ classes than cards because that's precisely the case that visitor pattern tries to mitigate - many offers, few cards.

@lascau2918 3 жыл бұрын

@mzma You are right but what if both cards and offers increase drastically what is the solution/pattern such that you obey the O from SOLID?

@mireazma 3 жыл бұрын

@@lascau2918 Not only O but I as well. Think about the case where a credit card only has certain offers or there's an offer that only applies to certain credit cards (it depends on how you look at it). The key is not enforcing all combinations, i.e. not enforce implementation of all those interface methods. I'm thinking we could modify the visitor part a bit. Abstract out individual card-offer combination into something like _Interaction_ that would have an _interact()_ method that does the calculation . _OfferVisitor_ would have a _List_ . I haven't thought this through but the idea behind this more complicated structure is: 1. Each new card doesn't imply modifying all offers. 2. Only have implementations for actual card-offer combinations, and not also for nonexistent combinations.

@rohitupadhyay9964 4 жыл бұрын

Awesome tutorial, thanks very much.

@ivannav 4 жыл бұрын

Great job!

@eliyahuspeyer1696 Жыл бұрын

your wonderful! thank you!

@ravikumaralabaka472 5 жыл бұрын

Thanks for detailed explanation

@ruixue6955 3 жыл бұрын

14:07 example of double dispatch (faking) - visitor 14:23 - 17:46 18:57 the concrete visitor: GasOffer, HotelOffer ... 19:32 CreditCard interface code 20:32 OfferVisitor 23:37 GasOfferVisitor

@tamilmanimuthusamy5506 5 жыл бұрын

Very good explanation

@kushal800 Жыл бұрын

best video. love from india

@ben6 3 жыл бұрын

This was the best resource I've found so far, but unsurprisingly, I am a bit confused. First: I guess we need to write a new `accept` method for each type of resource (e.g. offer) that Element can take (in this case, Bronze, SIlver, Gold credit cards.) We are not able to share `accept` methods between concepts: e.g. Not just offers (hotel, gas), but also other behaviour, like update state, get description, expiry. Could someone suggest a better name for accept? Second: The video author also wrote 'visitBronzeCreditCard' instead of just 'visit', so this actually goes around the problem of (not highlighting how visitor patterns overcomes lack of double dispatch)

@rsdntevl 5 жыл бұрын

Thanks for the intuitive example! a larger font would be great

@AnewbproMC 5 жыл бұрын

Amazing video! Thanks for the explanation

@jellyoful 5 жыл бұрын

Brilliant explanation.

@sv3167 3 жыл бұрын

Wow, pretty legit!! I understand!! Thanks a lot!

@dattatreykulkarni6472 4 жыл бұрын

Good Job Bro!!!

@JoshuaKisb 5 жыл бұрын

Wow. awesome video. great explanation. thank you

@stephane3115 5 жыл бұрын

great explanation!

@TheSimpleEngineer 5 жыл бұрын

Thanks, glad you enjoyed!

@jonathankee9322 Жыл бұрын

At around 13:00, we could have used instanceof and casting to get the correct Cat or Dog object though?

@atanubanerjee3389 3 ай бұрын

Hi Ryan - so could you please tell how I apply Visit/Accept pattern to resolve the original problem of cat-bark or dog-meow you originally started with ? Should I create one more class like CATDOG from Animal, accept runner request and forward to makeSound Visitor - visit(CATDOG). Or simply type-check a => in Dog "makeSound(Animal a)" for Runner request of "dog.makeSound(cat)" and take action . Much appreciate and thanx.