Ruby provides tools to access the source code of methods directly in the console. This is useful for debugging or understanding external libraries. Note: methods defined dynamically (common in Rails) might not expose their source.

Viewing Instance Method Source

To inspect an instance method, use instance_method on the class, followed by source:

Product.instance_method(:calculate_price).source
# => "  def calculate_price\n    base_price * discount_factor\n  end\n"

To improve readability, call display:

Product.instance_method(:calculate_price).source.display
# def calculate_price
#   base_price * discount_factor
# end
# => nil

Viewing Class (Singleton) Method Source

For class methods, replace instance_method with singleton_method:

Product.singleton_method(:find_by_sku).source
# => "  def find_by_sku(sku)\n    where(sku: sku).first\n  end\n"

Finding Methods Dynamically

If you’re unsure about a method’s name, filter methods using a regular expression.

Instance Methods

To list instance methods matching a pattern:

Order.instance_methods.grep(/total/)
# => [:calculate_total, :total_in_cents]

This finds all methods with “total” in their name.

Class Methods

For class methods, use singleton_methods with a regex:

Order.singleton_methods.grep(/export/)
# => [:export_to_csv, :export_to_pdf]