Identifying classes from requirements in LLD - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to identify the main class representing a person in the system.

LLD

class [1]:
    def __init__(self, name, age):
        self.name = name
        self.age = age

Drag options to blanks, or click blank then click option'

AOrder

BCar

CPerson

DProduct

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing unrelated class names like Car or Product.

The main entity representing a person is best named Person.

2fill in blank

medium

Complete the code to add an attribute representing a unique identifier for the class.

LLD

class Order:
    def __init__(self, [1], amount):
        self.order_id = [1]
        self.amount = amount

Drag options to blanks, or click blank then click option'

Aprice

Border_id

Cquantity

Dcustomer

Attempts:

3 left

💡 Hint

Common Mistakes

Using attributes like price or quantity as identifiers.

The unique identifier for an order is typically called order_id.

3fill in blank

hard

Fix the error in the class definition by choosing the correct method name for initialization.

LLD

class Product:
    def [1](self, name, price):
        self.name = name
        self.price = price

Drag options to blanks, or click blank then click option'

A__init__

B__start__

C__create__

D__new__

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect method names like __start__ or __create__.

The constructor method in Python classes is __init__.

4fill in blank

hard

Fill both blanks to define a class with an attribute and a method to display it.

LLD

class [1]:
    def __init__(self, [2]):
        self.[2] = [2]
    def display(self):
        print(self.[2])

Drag options to blanks, or click blank then click option'

ACustomer

Bemail

CProduct

Dprice

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing class names and attribute names incorrectly.

The class is Customer with an attribute email to display.

5fill in blank

hard

Fill all three blanks to create a class with an attribute, a method to update it, and a method to retrieve it.

LLD

class [1]:
    def __init__(self, [2]):
        self.[2] = [2]
    def update_[2](self, new_value):
        self.[2] = new_value
    def get_[2](self):
        return self.[2]

Drag options to blanks, or click blank then click option'

AAccount

Bbalance

Cemail

DCustomer

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing class and attribute names or using unrelated attributes.

The class Account has an attribute balance with update and get methods.

Practice

1. Which of the following is most likely a class when designing a library management system?

easy

A. Return

B. Borrow

C. Book

D. Search

Solution

1. Step 1: Identify nouns in the requirement

   Classes usually come from nouns. Here, 'Book' is a noun representing an object.

2. Step 2: Differentiate between nouns and verbs

   'Borrow', 'Return', and 'Search' are actions (verbs), so they are methods, not classes.

3. Final Answer:

   Book -> Option C

4. Quick Check:

   Class = Noun = Book [OK]

Hint: Pick the noun as class, verbs become methods [OK]

Common Mistakes:

• Choosing verbs as classes
• Confusing actions with objects
• Ignoring nouns in requirements

2. In a ride-sharing app, which of these is the correct way to represent a class in code?

easy

A. class Driver {}

B. function Driver() {}

C. var Driver = 5;

D. let driver = 'John';

Solution

1. Step 1: Understand class syntax in LLD context

   Classes are defined with the keyword 'class' followed by the class name.

2. Step 2: Check options for class declaration

   class Driver {} uses 'class Driver {}' which is correct syntax for a class.

3. Final Answer:

   class Driver {} -> Option A

4. Quick Check:

   Class syntax uses 'class' keyword [OK]

Hint: Look for 'class' keyword to identify class declaration [OK]

Common Mistakes:

• Using function instead of class
• Assigning class name to variable
• Confusing variables with classes

3. Given the requirement: "A hotel booking system must manage Guests, Rooms, and Bookings." Which of these is the correct set of classes identified?

medium

A. [Booking, Book, GuestList]

B. [Guest, Room, Booking]

C. [Guest, Book, RoomBooking]

D. [Room, Guest, ReservationList]

Solution

1. Step 1: Extract nouns from the requirement

   The nouns are Guests, Rooms, and Bookings, which represent objects.

2. Step 2: Match nouns to class names

   Classes should be singular nouns representing entities: Guest, Room, Booking.

3. Final Answer:

   [Guest, Room, Booking] -> Option B

4. Quick Check:

   Classes = Nouns = Guest, Room, Booking [OK]

Hint: Pick singular nouns as class names from requirements [OK]

Common Mistakes:

• Using verbs as classes
• Using plural or combined names incorrectly
• Adding unrelated terms

4. You have a requirement: "The system should allow Users to login and logout." Which of the following is an error in identifying classes and methods?

medium

A. Class: User; Methods: login(), logout()

B. Class: UserAccount; Methods: login(), logout()

C. Class: User; Methods: authenticate(), logout()

D. Class: Login; Methods: user(), logout()

Solution

1. Step 1: Identify nouns and verbs

   'User' is a noun (class), 'login' and 'logout' are actions (methods).

2. Step 2: Check option correctness

   Class: Login; Methods: user(), logout() incorrectly uses 'Login' as a class and 'user()' as a method, which reverses noun and verb roles.

3. Final Answer:

   Class: Login; Methods: user(), logout() -> Option D

4. Quick Check:

   Class = noun, Method = verb [OK]

Hint: Classes are nouns; methods are verbs [OK]

Common Mistakes:

• Using verbs as classes
• Naming methods as nouns
• Mixing class and method roles

5. A food delivery app requirement states: "Customers place Orders, Restaurants prepare Meals, and DeliveryAgents deliver Orders." Which classes should be created to model this system correctly?

hard

A. [Customer, Order, Restaurant, Meal, DeliveryAgent]

B. [Customer, PlaceOrder, Restaurant, Meal, Deliver]

C. [CustomerOrder, RestaurantMeal, Delivery]

D. [Order, Meal, DeliveryAgent, Place]

Solution

1. Step 1: Identify all nouns in the requirement

   Nouns are Customers, Orders, Restaurants, Meals, DeliveryAgents.

2. Step 2: Use nouns as class names and verbs as methods

   Classes should be Customer, Order, Restaurant, Meal, DeliveryAgent. Actions like 'place' and 'deliver' become methods.

3. Final Answer:

   [Customer, Order, Restaurant, Meal, DeliveryAgent] -> Option A

4. Quick Check:

   Classes = Nouns only, verbs become methods [OK]

Hint: Classes = nouns; actions = methods in those classes [OK]

Common Mistakes:

• Using verbs as classes
• Combining nouns incorrectly
• Omitting important entities