Welcome to the very first lesson of the "Clean Code with Multiple Classes in Ruby" course! 🎉 This course aims to guide you in writing code that's easy to understand, maintain, and enhance. Within the broader scope of clean coding, effective class collaboration is crucial for building well-structured applications. In this lesson, we will delve into the intricacies of class collaboration and coupling — key factors that can make or break the maintainability of your software. Specifically, we'll address some common "code smells" that indicate problems in class interactions and explore ways to resolve them.

Let's dive into the challenges of class collaboration by focusing on four common code smells:

• Feature Envy: Occurs when a method in one class is overly interested in methods or data in another class.
• Inappropriate Intimacy: Describes a situation where two classes are too closely interconnected, sharing private details.
• Message Chains: Refers to sequences of method calls across several objects, indicating a lack of clear abstraction.
• Middle Man: Exists when a class mainly delegates its behavior to another class without adding functionality.

Understanding these code smells will enable you to improve your class designs, resulting in cleaner and more maintainable code.

These code smells can significantly impact system design and maintainability. Let's consider their implications:

• They can lead to tightly coupled classes, making them difficult to modify or extend. 🔧
• Code readability decreases, as it becomes unclear which class is responsible for which functionality.

Addressing these issues often results in code that's not only easier to read but also more flexible and scalable. Tackling these problems can markedly enhance software architecture, making it more robust and adaptable.

Feature Envy occurs when a method in one class is more interested in the fields or methods of another class than its own. Here's an example in Ruby:

Ruby
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1class ShoppingCart
2  def initialize
3    @items = []
4  end
5  
6  def calculate_total_price
7    total = 0
8    @items.each do |item|
9      total += item.price * item.quantity
10    end
11    total
12  end
13end
14
15class Item
16  attr_accessor :price, :quantity
17  
18  def initialize(price, quantity)
19    @price = price
20    @quantity = quantity
21  end
22end

In this scenario, calculate_total_price in ShoppingCart overly accesses data from Item, indicating feature envy.

To refactor, consider moving the logic to the Item class:

Ruby
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1class ShoppingCart
2  def initialize
3    @items = []
4  end
5  
6  def calculate_total_price
7    total = 0
8    @items.each do |item|
9      total += item.calculate_total
10    end
11    total
12  end
13end
14
15class Item
16  attr_accessor :price, :quantity
17  
18  def initialize(price, quantity)
19    @price = price
20    @quantity = quantity
21  end
22  
23  def calculate_total
24    price * quantity
25  end
26end

Now, each Item calculates its own total, reducing dependency and distributing responsibility appropriately. ✔️

Inappropriate Intimacy occurs when a class is overly dependent on the internal details of another class. Here's an example in Ruby:

Ruby
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1class Library
2  def initialize(book)
3    @book = book
4  end
5
6  def print_book_details
7    puts "Title: #{@book.title}"
8    puts "Author: #{@book.author}"
9  end
10end
11
12class Book
13  attr_accessor :title, :author
14  
15  def initialize(title, author)
16    @title = title
17    @author = author
18  end
19end

In this scenario, the Library class relies too heavily on the details of the Book class, demonstrating inappropriate intimacy.

To refactor, allow the Book class to handle its own representation:

Ruby
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1class Library
2  def initialize(book)
3    @book = book
4  end
5
6  def print_book_details
7    puts @book.details
8  end
9end
10
11class Book
12  attr_accessor :title, :author
13  
14  def initialize(title, author)
15    @title = title
16    @autor = author
17  end
18  
19  def details
20    "Title: #{title}\nAuthor: #{author}"
21  end
22end

This adjustment enables Book to encapsulate its own details, encouraging better encapsulation and separation of concerns. 🛡️

Message Chains occur when classes need to traverse multiple objects to access the methods they require. Here's a demonstration in Ruby:

Ruby
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1class User
2  attr_accessor :address
3
4  def initialize(address)
5    @address = address
6  end
7end
8
9class Address
10  attr_accessor :zip_code
11
12  def initialize(zip_code)
13    @zip_code = zip_code
14  end
15end
16
17class ZipCode
18  def self.postal_code
19    "90210"
20  end
21end
22
23# Usage
24user = User.new(Address.new(ZipCode))
25postal_code = user.address.zip_code.postal_code

The chain user.address.zip_code.postal_code illustrates this problem.

To simplify, encapsulate the access within methods:

Ruby
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1class User
2  attr_accessor :address
3
4  def initialize(address)
5    @address = address
6  end
7  
8  def user_postal_code
9    address.postal_code
10  end
11end
12
13class Address
14  attr_accessor :zip_code
15  
16  def initialize(zip_code)
17    @zip_code = zip_code
18  end
19  
20  def postal_code
21    zip_code.postal_code
22  end
23end
24
25class ZipCode
26  def self.postal_code
27    "90210"
28  end
29end
30
31# Usage
32user = User.new(Address.new(ZipCode))
33postal_code = user.user_postal_code

This adjustment makes the User class responsible for retrieving its postal code, creating a clearer and more direct interface. 📬

A Middle Man problem occurs when a class primarily exists to delegate its functionalities. Here's an example in Ruby:

Ruby
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1class Controller
2  def initialize(service)
3    @service = service
4  end
5
6  def execute
7    @service.perform_action
8  end
9end
10
11class Service
12  def perform_action
13    # Action performed
14  end
15end

The Controller doesn't do much beyond delegating to Service.

To refactor, simplify delegation or reassign responsibilities:

Ruby
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1class Service
2  def perform_action
3    # Action performed
4  end
5end
6
7# Usage
8service = Service.new
9service.perform_action

By removing the unnecessary middleman, the design becomes more streamlined and efficient. 🔥

In this lesson, you've explored several code smells associated with suboptimal class collaboration and coupling, including Feature Envy, Inappropriate Intimacy, Message Chains, and Middle Man. By identifying and refactoring these smells, you can elevate your code's clarity and maintainability.

Get ready to put these concepts into practice with upcoming exercises, where you'll identify and refactor code smells, strengthening your skills. Keep striving for cleaner, more effective code! 🌟