Why metaprogramming is powerful in Ruby - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a method dynamically using define_method.

Ruby

class Greeting
  [1] :hello do
    puts 'Hello, world!'
  end
end

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

Amethod_missing

Bdef

Cattr_accessor

Ddefine_method

Attempts:

3 left

💡 Hint

Common Mistakes

Using def instead of define_method for dynamic method creation.

The define_method lets you create methods dynamically, which is a key part of Ruby metaprogramming.

2fill in blank

medium

Complete the code to catch calls to undefined methods using method_missing.

Ruby

class Dynamic
  def [1](method_name, *args)
    puts "You called #{method_name} with #{args.inspect}"
  end
end

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

Arespond_to_missing?

Bmethod_missing

Cdefine_method

Dsend

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing method_missing with respond_to_missing? or send.

method_missing is a Ruby hook that lets you handle calls to methods that don't exist, enabling dynamic behavior.

3fill in blank

hard

Fix the error in the code to dynamically create getter methods using define_method.

Ruby

class Person
  [:name, :age].each do |attr|
    [1] attr do
      @#{attr}
    end
  end
end

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

Adef

Battr_accessor

Cdefine_method

Dattr_reader

Attempts:

3 left

💡 Hint

Common Mistakes

Using def inside a block, which is invalid syntax.

define_method is used here to create getter methods dynamically for each attribute.

4fill in blank

hard

Fill both blanks to create a method that responds to any undefined method by printing its name and arguments.

Ruby

class Catcher
  def [1](method_name, *args)
    puts "Called #{method_name} with #{args[2]"
  end
end

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

Amethod_missing

Binspect

Cjoin

Dto_s

Attempts:

3 left

💡 Hint

Common Mistakes

Using to_s instead of inspect for argument display.

method_missing catches undefined method calls, and inspect shows the arguments nicely.

5fill in blank

hard

Fill all three blanks to create a dynamic attribute writer method using define_method.

Ruby

class DynamicAttr
  [:title, :author, :year].each do |attr|
    [1] "#{attr}=" do |value|
      @[2] = [3]
    end
  end
end

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

Adefine_method

Battr

Cvalue

Dattr_accessor

Attempts:

3 left

💡 Hint

Common Mistakes

Using attr_accessor instead of define_method for dynamic method creation.

This code dynamically creates setter methods for each attribute. define_method defines the method, attr is the attribute name used for the instance variable, and value is the argument assigned to the instance variable.