Example 1: Simplified Online Shopping Cart
Interactive Audio Lesson
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Introduction to the Shopping Cart Design
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Today, we're going to look at designing an online shopping cart. First, can anyone tell me what a shopping cart does?
It lets customers add products they want to buy.
Exactly! Now let's dive into the core classes we'll use to build this cart. What do you think are some important classes?
Maybe a Customer class to represent the users?
That's a great start! We'll also need a Product class, right? Can anyone think of attributes for these classes?
The Customer class can have a name and email, and the Product class might need a name and price.
Great observations! This establishes our base structure. Remember, classes are like blueprintsβitβs essential to get them right before building.
So, summarizing this session, we discussed the core classes: Customer and Product, and their important attributes.
Understanding Relationships
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Now that we have our classes, let's discuss the relationships between them. Can anyone tell me how the Customer and Order are related?
A Customer can place many Orders.
Exactly! This is a one-to-many relationship. What about the ShoppingCart's relationship with CartItems?
The ShoppingCart contains multiple CartItems.
Correct! Thatβs using composition. What happens to the CartItems if we delete the ShoppingCart?
They get deleted as well because they are owned by it.
Exactly right! Establishing these relationships accurately helps in both design and implementation. Can anyone share a summary of what we've learned today?
We learned about the relationships between Customer, Orders, and ShoppingCart with their corresponding relationships.
Core Methods of Classes
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Letβs delve into what actions our classes can perform. What methods do you think the Customer class should have?
It should have a method to add products to the cart.
Correct! The method `addToCart()` is vital. What about the methods in the ShoppingCart?
It might have `addItem()` and `removeItem()` methods.
Absolutely! These methods let users manage items in their cart. Letβs also think about the Order class. What methods would be necessary there?
It needs a checkout method for finalizing the order.
Yes, `checkout()` is crucial for processing the purchase. To wrap up, could someone summarize our key findings about class methods?
We identified important methods like `addToCart()`, `addItem()`, `removeItem()`, and `checkout()` for different classes.
Good Design Principles
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Now that we've structured our classes and their interactions, let's focus on good design principles. How important is encapsulation?
It's important because it protects the data within a class.
Exactly! Keeping data private ensures consistency. What about cohesion?
High cohesion means each class should really focus on a single responsibility, right?
That's right! And how does low coupling play a role in maintaining class interaction?
Low coupling means classes should be independent but still communicate when needed.
Correct! Each principle helps create maintainable and scalable software. Let's summarize what we've learned about design principles.
We discussed encapsulation, high cohesion, low coupling, and their importance in software design.
Introduction & Overview
Read summaries of the section's main ideas at different levels of detail.
Quick Overview
Standard
The section offers a detailed breakdown of the design of a simplified online shopping cart, describing the core classes and their properties. It emphasizes relationships and interactions, showcasing the principles of object-oriented design in a practical context.
Detailed
Detailed Summary
This section provides a comprehensive overview of designing a simplified online shopping cart software application. The design revolves around several core classes, including Customer, Product, ShoppingCart, CartItem, Order, OrderItem, and PaymentGateway. Each class has specific attributes and behaviors, which help maintain the order processing workflow effectively.
- Classes:
- Customer: Represents a customer with attributes such as
customerID,name,email, andpassword. It includes methods likeaddToCart()andplaceOrder(), reflecting users' actions in the shopping process. - Product: Represents items available for sale, featuring attributes like
productID,name,description,price, andstockQuantity. - ShoppingCart: Contains a list of
CartItems, allowing customers to manage their desired products. Essential methods includeaddItem(),removeItem(), andcheckout(). - CartItem: Represents a particular product in the cart with its quantity.
- Order: Captures details of a completed purchase with attributes like
orderID,orderDate,customer, and a total amount. - OrderItem: Similar to
CartItem, but for finalized orders, providing a permanent record of purchased products. - PaymentGateway: An external entity that handles payments during the checkout process.
The section also explores relationships among these classes:
- A Customer can place multiple Orders.
- A ShoppingCart comprises multiple CartItems, showcasing composition.
- Order consists of multiple OrderItems, continuing the principle of composition.
- Both CartItem and OrderItem are linked to Product, reflecting simple associations.
Inheritance is also highlighted, for instance, differentiating between various payment methods (e.g., CreditCardPayment and NetBankingPayment) derived from an abstract class PaymentMethod. The section concludes with good design principles, illustrating concepts like encapsulation, high cohesion, low coupling, and separation of concerns that ensure a robust software design.
Key Concepts
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Object-oriented design: A method of software design using classes and objects.
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Class: A blueprint for creating objects, encapsulating data and behaviors.
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Encapsulation: The principle of restricting access to certain components of an object.
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Cohesion: The degree to which the elements inside a module belong together.
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Coupling: The degree of interdependence between modules.
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Composition: A design principle where a class is composed of one or more classes.
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Inheritance: A mechanism by which one class can inherit the attributes and methods from another.
Examples & Applications
A Customer adds a product to their ShoppingCart using the addToCart() method.
When the customer proceeds to checkout, the system creates an Order containing all CartItems.
Memory Aids
Interactive tools to help you remember key concepts
Rhymes
In a ShoppingCart so bright, Customers select with delight, Products gathered, ready to pay, Orders placed without delay.
Stories
Imagine a bustling online store where a customer named Alex walks in, adding a beautiful vase to his ShoppingCart. He pays effortlessly through the PaymentGateway, and the vase becomes a treasure in his Order.
Memory Tools
Remember the classes: C-ustomer, P-roduct, S-hoppingCart, C-artItem, O-rder, O-rderItem, P-aymentGateway as the CPSC-COP to navigate the shop!
Acronyms
To remember our class relationships, think of the acronym RPC
for Relationships
for Products
for CartItems!
Flash Cards
Glossary
- Customer
Represents the user of the shopping cart, holding attributes like customer ID and methods for cart actions.
- Product
Represents items available for sale, featuring attributes like product ID, name, and price.
- ShoppingCart
Holds the CartItems for a customer and provides methods to manage those items.
- CartItem
Represents a product in the ShoppingCart along with its quantity.
- Order
Represents a completed transaction, including details like order ID, total amount, and customer.
- OrderItem
Similar to CartItem, but used in finalized orders, containing information about purchased products.
- PaymentGateway
External service for processing payments in the order placement process.
Reference links
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