Module_eval for dynamic behavior in Ruby - Mini Project: Build & Apply

Using Module_eval for Dynamic Behavior in Ruby

📖 Scenario: Imagine you are building a simple system where you want to add new behaviors to a class dynamically. This means you can add new methods to a class while the program is running, just like adding new tools to a toolbox whenever you need them.

🎯 Goal: You will create a Ruby class and then use module_eval to add a new method dynamically. Finally, you will call that method to see it work.

📋 What You'll Learn

Create a class called Toolbox

Create a string variable called method_code that contains Ruby code for a method named greet

Use module_eval on the Toolbox class to add the greet method dynamically

Create an instance of Toolbox and call the greet method to print the greeting

💡 Why This Matters

🌍 Real World

Dynamic method addition is useful when you want to add features to classes without changing their original code, such as plugins or extensions in software.

💼 Career

Understanding <code>module_eval</code> helps in metaprogramming tasks, which are valuable skills for Ruby developers working on flexible and maintainable codebases.

1

Create the Toolbox class

Create a class called Toolbox with no methods inside.

Ruby

# Create the Toolbox class
# Your code here

Need a hint?

Use the class keyword followed by Toolbox and end to define the class.

2

Create the method code string

Create a string variable called method_code that contains the Ruby code for a method named greet. The method should print "Hello from Toolbox!" when called.

Ruby

class Toolbox
end

# Create the method_code string with the greet method
# Your code here

Need a hint?

Use double quotes for the string and escape the newline with \n. The method should be named greet and print the greeting.

3

Use module_eval to add the greet method

Use module_eval on the Toolbox class with the method_code string to add the greet method dynamically.

Ruby

class Toolbox
end

method_code = "def greet\n  puts 'Hello from Toolbox!'\nend"

# Use module_eval on Toolbox with method_code
# Your code here

Need a hint?

Call module_eval on the Toolbox class and pass method_code as the argument.

4

Create an instance and call the greet method

Create an instance of Toolbox called box and call the greet method on it to print the greeting.

Ruby

class Toolbox
end

method_code = "def greet\n  puts 'Hello from Toolbox!'\nend"

Toolbox.module_eval(method_code)

# Create an instance box and call greet
# Your code here

Need a hint?

Create a new object with Toolbox.new and call greet on it.