4. Decorator Design Pattern Explanation with Java Coding, LLD System Design, System design interview 

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bhai ne kuch videos paid kr di 😁

Glad it helped!

Welcome

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👍

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Thank you Yash, not sure if youtube does not show playlist title and description, i have mentioned in both the place that Start from bottom and move Upward, let me check

Thank you

:)

Glad to hear that

Thanks paji

public class PizzaShop { public static void main(String[] args) { BasePizza base = new VegDelight(); System.out.println(base.cost()); BasePizza customPizza = new ExtraCheese(new Mushroom(new Farmhouse())); System.out.println(customPizza.cost()); } }

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Thanks there is a complete in depth playlist Manashi:)

@@ConceptandCoding Yes am checking. Thanks again for the content.

Thanks a lot buddy but call me Shrayansh, we both are students,let's keep learning and sharing

Thanks Saifur

thank you Prashant. means lot to me.

Thank you so much!

Thank you

Thanks

Thanks buddy

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Noted, will do it from now

Thank you, sure let me check

Thank you

I think in 1 video i did that Vivek, if not then do check the first video of "Live LLD" playlist in that i must have explained it

Here is the timestamp ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE--UjjfzJ574w.html to understand "IS-A" and "HAS-A" relationship

Thank you

@@ConceptandCoding

You have created A,B C different concrete classes. If you want to create new concrete classes with properties of lets say B , with decorator pattern you will have B1 , B2 etc. But without decorator pattern you might have to write more code to not only include the property of B but also its own new property. I hope this helps.

Yes will work on old video, but all latest videos are in English only

Hope you will find the content useful 🙏

Correct, if you want this pattern and design car with this way. Then you are right

kind of you can say, but thats a good thinking

Exactly. I have the same question in my mind.

:)

Ack. Will get back to you by eod

By the Dependency Inversion Principle classes should depend on interfaces or abstract classes rather than concrete classes.

I have the same question. Since the Pizza problem comes more in a object creational use case, wouldn't builder pattern fit more for this use case. Decorators are used to modify the functionality of an object in runtime. Using decorator for object creation puts the object in an inconsistent state till all the decorators are completed. In real scenarios, decorator would be useful, when we need to stack up the operations like encoding a file and then compressing etc.

thanks a lot buddy for super thanks 🙏

@@ConceptandCodinghello sir , i want to become member so I can access all your videos of this lld series. Please tell me the process

at channel home page you will find the join button, there you can join “Unlock LLD, HLD..” one

@@ConceptandCoding thanks joined

When you want 100% abstraction go for interface, else go for Abstract class

Yes, i know this, but while in interview when we say that i will create an abstract class or interface or concrete class they always ask why so? Why not interface inplace of abstract class, this is has been asked alot. So just a request when ever u make any any interface or abstract class please tell us the why interface or abstract please 🙏

So here inheritance is only used for type matching and composition is used to get the behaviour.

It will give us flexibility in future

When it will be completed it will be difficult for me to say. I am going with 1 video a week for now. But i am consistent

Generally both purpose is same to hide the implementation. Interface provide 100% abstraction, while in abstract class you can also implement some methods which are common to child classes

could you please try to implement it and see what challenge you are facing.

Hi Prashant, to unlock LLD questions, you need "Unlock LLD, HLD, Java" membership level. I think currently you have taken "Appreciation" level one.

had the same question

Yes we can, if you don't want to implement any common method in that

can you implement and show how for the same example which i took.

@@ConceptandCoding sure

from __future__ import annotations from abc import ABC, abstractmethod import enum import string from typing import List class ToppingList(enum.Enum): extra_cheese = 20.00 jalapeno = 30.00 mushroom = 10.00 chicken_tikka = 60.00 class BasePizza(ABC): @abstractmethod def get_ingregents(self) -> List: pass @abstractmethod def cost(self) -> float: pass # concrete pizza class class MargaritaPizza(BasePizza): ingredients: List = ['Cheese','Bread','Olive Oil'] def get_ingregents(self) -> List: return self.ingredients def cost(self) -> float: return 150.00 class VeggiePizza(BasePizza): ingredients: List = ['Cheese','Bread','Olive Oil','Veggies'] def get_ingregents(self) -> List: return self.ingredients def cost(self) -> float: return 200.00 class Topping(BasePizza): _base_pizza: BasePizza = None def __init__(self,base_pizza: BasePizza, topping:string) -> None: self._base_pizza = base_pizza self._topping = topping def get_ingregents(self) -> List: base_ingregents = self._base_pizza.get_ingregents() base_ingregents.append(self._topping) return base_ingregents def cost(self) -> float: return self._base_pizza.cost() + ToppingList[self._topping].value if __name__ == '__main__': base_pizza = MargaritaPizza() margarita_pizza_extra_cheese = Topping(base_pizza,'extra_cheese') print(margarita_pizza_extra_cheese.get_ingregents()) print(margarita_pizza_extra_cheese.cost()) margarita_pizza_extra_cheese_jalapeno = Topping(margarita_pizza_extra_cheese,'jalapeno') print(margarita_pizza_extra_cheese_jalapeno.get_ingregents()) print(margarita_pizza_extra_cheese_jalapeno.cost())

@@ConceptandCoding Hey does the below solution follow any anti pattern wrt to decorator design pattern

this code still maintains 'is-a' and 'has-a' relationship. So that is the requirement of decorator pattern . But here my concern with enum is not decorator pattern but with scalability and managebility lets say i want to add more methodd apart from Cost method like TotalCalories, totalProtein , totalCarbs etc. (lets say 10 -20 methods like this) how easy with enum to support this.

Thank you. See it's a very valid question, nobody can remember all these designs patterns. Couple of things: - How many design patterns is sufficient? Very difficult to answer, what interviewer can ask, we don't know right. - How to remember all? We don't have to, just try to implement design patterns with your own examples, whatever examples i used take it as a reference and then try to implement with different example. It will help you to remember in which usecase what has to be done. Keep 5-6 design patterns on your finger tips which is very frequently asked.

@@ConceptandCoding Thanks a lot Sir for the quick and detailed response!!

okay, could you please tell me, how you would solve the scenario where you have 1000s of combination like BasePizze, BasePizze + cheese , BasePizza + mushroom, Veggie + cheese and go on...... The biggest advantage decorator pattern adds up is control on number of classes if there are so so many combinations possible.

@@ConceptandCoding Thanks for your reply. Lets suppose Base pizza is extended by two Pizza class Veg and Non Veg Pizza. I have another ExtraAddOn class which is inherited by say cheese, mushroom, paneer and so on ... Now, I have a " vector extraList; " in Veg and Non Veg Pizza class. So, whatever combinations of ExtraAddOn you need, you can add to that list and calculate cost. Only thing is that you cannot mix the base Pizza options, but i don't think that's the requirement here. Am i thinking it wrong ?

same question . Can anyone explain same @Concept && Coding - by Shrayansh

We can call the topping decorator only right

If you want some method to implement in base class which child can reuse, then go for abstract else interface.

@@ConceptandCoding tysm 🙏

I think main task of Strategy Pattern is to remove redundant code where as Decorator Pattern is used to solve the problem of maintainability of our classes.