I think it is obvious that Lesson class should have responsibility of calculating discount. Seeing other comments, sure if there is a discount on total amount, then that one will fall under Cart's responsibility. But to calculate individual lesson's discount, if we think that Cart should have that responsibility, that would mean Cart would have to create something like getLessonDiscount(lesson) and things would get weird in getTotalAmount(). Instead, Lesson should have getDiscount() and then there can be a getPrice() function in Lesson that returns getFees()-getDiscount() and Cart's getTotalAmount() can iterate through each lesson in cart and call its getPrice() function to calculate total amount, not caring about how it works internally.
Agreed. This is where i think GRASP (General Responsibility Assignment Software Patterns/Principles) comes in handy. There's one principle in GRASP called "Information Expert" that's suitable for this particular case.
i think there can be two types of discount , one on individual item or one on total item which can be seasonal or weekly sale for total amount , its possible we would also need a date or day for that so also in slot class .
I think there would be three cases, * The discount is same for all course : then we will add it CART * Each course will have their own discounts (If any popular course is there it would have less discount and if any new one is there, it would have more discount) : then we will add discount in LESSON * Combination of both what you think?
@@happyverma91 the question is: which class will calculate the discount of a particular LESSON - obviously the LESSON class. Try to apply the knowledge you learned (abstraction & encapsulation). When I call lesson.getFees(), I dont care how it was calculated, just give me the prices so that I can sum them up. Dont tell me to get the base fee and get the discount code and apply the discount etc... it is doable, but is against abstraction and it's bad code
@@linhvu407 @happyverma91 They main keyword here in the question asked is "PARTICULAR LESSON" which signifies the responsibility to be of the Lesson class. Had this been a general question of applying discount, it should belong to cart class.
I feel that totalAmount() will calculate the sum of each lesson price after the discount if each lessons has a discount price seperately. Getdiscount() method should be implemented in cart class so that if the user has some coupons this method will be called and calculate the discount price. Lesson has should have the attributes of discount price or discounts percentage and actual price.
Discounts should be calculated in the Cart Class as after adding items to the cart when the user would be purchasing the lessons the system will prompt a message of whether user wants to take discount or not. Anyways thanks for the wonderful series 🌻♥️
But the question was asked to calculate the discount on particular lessons only. So, according to you, will there be any id given to each lesson, according to that id the getTotalAmount() in the Cart class will calculate the total amount with discount?
09:32 The Responsibility of calculating the discount should be with the Cart Class. Reasons: 1. From a business point of view, discounts are applied when we make bulk purchases or purchase over a certain limit. Since all these calculations are there inside the cart class, so, it is wiser to keep this inside cart class only 2. Also, Business runs combo offers, where if two particular products are purchased, the discount is applied, so, even this information is already there in the cart class, hence, the discount is better placed in the cart. Doing this, also hold the abstraction principle, as some other class need not know, what are items added and how the total price is calculated. The cart class can simply return the net payment amount after discount to the user, who will then check out by making payment. PS: Any corrections/ alternate views are welcome.
It depends on use cases. There can be multiple types of discounts. Discount on item level, coupon discount, seller discount etc. only the discounts which can be applied on the whole cart irrespective of the seller or item can be kept in cart. The entity specific discounts like item or seller or coupon shall only reside with those entities. For eg: if the item search has to show discount on items, and discount is stored in cart, how would the item discount be displayed ? It won’t fall cart because cart would be empty at that time.
I think discount should be in cart class as in that class we can calcute the discount of individual lesson added and and total discount can also be calculated after calculating individual discount of all lesson.
I think the answer to the question depends on the type of application we are developing. If our application logic provides a discount for each lesson separately then we should implement it in lesson class as a user can be using multiple coupon codes for different lessons, and the cart has to have the member for which code which lesson gets a discount, but if we provide discount on the whole cart then it should be the responsibility of cart class to handle discount, or we can give the responsibility of specific lesson to lesson class and for the whole cart to cart class. We can also make a separate class for disscount which takes the coupon code and gives back the discounted price. please comment and tell me if any mistakes in my solution.
Should our entity classes have methods like calculateDiscount or even makePayment() ? Because in real scenarios we generally have the service classes which implement these kinds of methods as any kind of business logic should ideally stay away from entity/beans. We just use these beans/entities to store the state. Please let me know if there is something wrong with my understanding.
In the problem she asked the discounts can be part of lessons class also we can have some discounts on particular lessons as well as we can have cart discounts like after a certain amount a discount is applied so can we implement an interface of discounts and use them in both the classes. Can you please correct me if wrong?
If we want to give discount on total amount then implement discount method in cart so that lessons class do not know about total amount And if we want to give discount based on lesson price and not on total amount then implement the discount method in lessons class and expose getPriceAfterDiscount method instead of price method to that cart class in this way cart will not know about price of lessons instead it will directly know the discounted price
There may also be a case that discount on total price can be done on cart class, and the lessons eligible for discounts can be figured out by a method present in lesson class like isDiscountable() Ofcourse all in all, it would reside in cart class if its total based, but can have internal calls in itself as well @sudoCode are the above two comments good for discussion in interviews, or we can be oversharing or something like that which can give negative impact?
Could you please clarify why credit card and payment can't have "Has-a" relationship as aggregation? A payment can be done using credit/debit card, netbanking, upi or through cash. But a credit card will always be used to make payment.
I would refer to GRASP (General Responsibility Assignment Software Patterns/Principles) coined by Craig Larman that I personally think would be useful in terms of the object/class responsibilities.
Thank you for this course. Can you please advise me on what book should I buy to learn Class Responsibility and Abstraction/Encapsulation to be able to design like you on this video?
Payment can be done via credit card or debit card or netbanking. So payment will have one of the ways to get payment done. Hence payments has the info of how the payment is done and that’s by credit card.
@@sudocode sorry, still not clear😅. So shouldn't debit cards, credit cards and net banking be inherited from payment as different forms or types of payments ?
As per my understanding, Payment is one of the function performed by credit card or debit card. They are not type of payment, but payment is one of the function of these classes. From customer class as part of checkout method we should do something like creditcard.makePayment
Just had quick question regarding the relation b/w Credit card and payment. How should we implement this in our code , show we pass it as constructor of another class? Could you please suggest. Thank you!
I think it is obvious that Lesson class should have responsibility of calculating discount. Seeing other comments, sure if there is a discount on total amount, then that one will fall under Cart's responsibility. But to calculate individual lesson's discount, if we think that Cart should have that responsibility, that would mean Cart would have to create something like getLessonDiscount(lesson) and things would get weird in getTotalAmount(). Instead, Lesson should have getDiscount() and then there can be a getPrice() function in Lesson that returns getFees()-getDiscount() and Cart's getTotalAmount() can iterate through each lesson in cart and call its getPrice() function to calculate total amount, not caring about how it works internally.
Agreed. This is where i think GRASP (General Responsibility Assignment Software Patterns/Principles) comes in handy. There's one principle in GRASP called "Information Expert" that's suitable for this particular case.
i think there can be two types of discount , one on individual item or one on total item which can be seasonal or weekly sale for total amount , its possible we would also need a date or day for that so also in slot class .
@@CodeTillEternity i think the same ,thats how myntra , swiggy and other platforms work
first video where I got clear distinction between composition and aggregation with example. Thank you so much.
10 mins of video cleared out 10 hours of my time. Great work!
wow! looks like best video of LLD series..keep going.. hats off!
I think there would be three cases,
* The discount is same for all course : then we will add it CART
* Each course will have their own discounts (If any popular course is there it would have less discount and if any new one is there, it would have more discount) : then we will add discount in LESSON
* Combination of both
what you think?
I feel the lesson class will have the discount method, as each lesson might have a different discount percentage.
Discount can happen on your amount payable so it should be in cart class
But lesson can have seprate discount code
@@happyverma91 the question is: which class will calculate the discount of a particular LESSON - obviously the LESSON class.
Try to apply the knowledge you learned (abstraction & encapsulation). When I call lesson.getFees(), I dont care how it was calculated, just give me the prices so that I can sum them up. Dont tell me to get the base fee and get the discount code and apply the discount etc... it is doable, but is against abstraction and it's bad code
@@linhvu407 @happyverma91 They main keyword here in the question asked is "PARTICULAR LESSON" which signifies the responsibility to be of the Lesson class. Had this been a general question of applying discount, it should belong to cart class.
I really loved this video. Plain and simple but easy to digest hard concepts. Subscribed as well :)
Thank you so much. This was my last minute prep and I got placed in my dream company ❤️
Thanks a lot for such a great animation and explanation, it made it really to understand quite easily for the topics which seems to be hard to grasp!
I feel that totalAmount() will calculate the sum of each lesson price after the discount if each lessons has a discount price seperately. Getdiscount() method should be implemented in cart class so that if the user has some coupons this method will be called and calculate the discount price. Lesson has should have the attributes of discount price or discounts percentage and actual price.
Discounts should be calculated in the Cart Class as after adding items to the cart when the user would be purchasing the lessons the system will prompt a message of whether user wants to take discount or not. Anyways thanks for the wonderful series 🌻♥️
But the question was asked to calculate the discount on particular lessons only. So, according to you, will there be any id given to each lesson, according to that id the getTotalAmount() in the Cart class will calculate the total amount with discount?
09:32 The Responsibility of calculating the discount should be with the Cart Class.
Reasons:
1. From a business point of view, discounts are applied when we make bulk purchases or purchase over a certain limit. Since all these calculations are there inside the cart class, so, it is wiser to keep this inside cart class only
2. Also, Business runs combo offers, where if two particular products are purchased, the discount is applied, so, even this information is already there in the cart class, hence, the discount is better placed in the cart.
Doing this, also hold the abstraction principle, as some other class need not know, what are items added and how the total price is calculated. The cart class can simply return the net payment amount after discount to the user, who will then check out by making payment.
PS: Any corrections/ alternate views are welcome.
It depends on use cases. There can be multiple types of discounts. Discount on item level, coupon discount, seller discount etc. only the discounts which can be applied on the whole cart irrespective of the seller or item can be kept in cart. The entity specific discounts like item or seller or coupon shall only reside with those entities. For eg: if the item search has to show discount on items, and discount is stored in cart, how would the item discount be displayed ? It won’t fall cart because cart would be empty at that time.
Great Explanation! Please keep them coming!
Thanks for making this LLD Series
Thank you .....for sharing the LLD Knowledge.
It's a great help.🙏
I think discount should be in cart class as in that class we can calcute the discount of individual lesson added and and total discount can also be calculated after calculating individual discount of all lesson.
I think the answer to the question depends on the type of application we are developing. If our application logic provides a discount for each lesson separately then we should implement it in lesson class as a user can be using multiple coupon codes for different lessons, and the cart has to have the member for which code which lesson gets a discount, but if we provide discount on the whole cart then it should be the responsibility of cart class to handle discount, or we can give the responsibility of specific lesson to lesson class and for the whole cart to cart class. We can also make a separate class for disscount which takes the coupon code and gives back the discounted price.
please comment and tell me if any mistakes in my solution.
Thanks a lot sister, you are doing a great job to help us understand OOPS.
Its quite helpful to clear the fundamentals which will impact to crack many big concepts thanks keep doing love to learn from u guys 👍👍
Should our entity classes have methods like calculateDiscount or even makePayment() ? Because in real scenarios we generally have the service classes which implement these kinds of methods as any kind of business logic should ideally stay away from entity/beans. We just use these beans/entities to store the state. Please let me know if there is something wrong with my understanding.
You are right. It depends on service complexity and the architectural practices followed.
Ans to her question is at 8:51
In the problem she asked the discounts can be part of lessons class also we can have some discounts on particular lessons as well as we can have cart discounts like after a certain amount a discount is applied so can we implement an interface of discounts and use them in both the classes.
Can you please correct me if wrong?
Amazing, Thank you for sharing the knowledge..
Thank you so much for such a good explaination. great video.
If we want to give discount on total amount then implement discount method in cart so that lessons class do not know about total amount
And if we want to give discount based on lesson price and not on total amount then implement the discount method in lessons class and expose getPriceAfterDiscount method instead of price method to that cart class in this way cart will not know about price of lessons instead it will directly know the discounted price
There may also be a case that discount on total price can be done on cart class, and the lessons eligible for discounts can be figured out by a method present in lesson class like isDiscountable()
Ofcourse all in all, it would reside in cart class if its total based, but can have internal calls in itself as well
@sudoCode are the above two comments good for discussion in interviews, or we can be oversharing or something like that which can give negative impact?
Great videos!
Thank you so much great work
This is a really nice series.
Wow sudocode, you explains concept so well.
Could you please clarify why credit card and payment can't have "Has-a" relationship as aggregation? A payment can be done using credit/debit card, netbanking, upi or through cash. But a credit card will always be used to make payment.
I love you. Perfect tuts
Well thoughtful video got to learn lots of insights ... thanks mam 😊
Hi, I'm a new subcriber!!
A very impormative video. Thank you!
I would refer to GRASP (General Responsibility Assignment Software Patterns/Principles) coined by Craig Larman that I personally think would be useful in terms of the object/class responsibilities.
Thank you for this course. Can you please advise me on what book should I buy to learn Class Responsibility and Abstraction/Encapsulation to be able to design like you on this video?
There is a video on the channel where I recommended 5 books. Please check that
could you take an example and explain how to design/code it up from scratch using design principles?
Ma'am I want to become a system gesigner..so what's the 1st..step ..pls tell me and how to do prepare..my self about system designe..
if discount is of a particular lesson then it should be present in lesson class and then one can have getActualPrice getSellPrice and getDiscount.
Keep going 💫
Lesson class should have the responsibility of calculating the discount, and the cart class should get the discounted final price.
Great Content as Always. Keep making such videos. Thanks for helping engineers :)
discount should be applied here on the cart side.
Can you please append some numbers to know the series please?
Good suggestion
The best of best
Can anyone help me with understanding the credit card and payment relation.
Thank you❤
I think solving this amount-discount will be replicated for each lesson so it's better to do this task in cart once.
Isn't credit card a type of payment?, so shouldn't it be is-a with payment ?
Payment can be done via credit card or debit card or netbanking. So payment will have one of the ways to get payment done. Hence payments has the info of how the payment is done and that’s by credit card.
@@sudocode sorry, still not clear😅. So shouldn't debit cards, credit cards and net banking be inherited from payment as different forms or types of payments ?
As per my understanding, Payment is one of the function performed by credit card or debit card. They are not type of payment, but payment is one of the function of these classes. From customer class as part of checkout method we should do something like creditcard.makePayment
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Great
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- Rahul Balani
right
Just had quick question regarding the relation b/w Credit card and payment. How should we implement this in our code , show we pass it as constructor of another class? Could you please suggest. Thank you!
You can use strategy pattern to implement it.
Pro tip: play video at 0.75x speed
your speed of talking too fast . Normal spped is looking like 1.5x. Now i am on .75x😀😀😀😀
It’s my brain that thinks fast and hence the words 😎
@@sudocode And here I'm playing this video at 1.75x