Comments

Ruby has two types of comments: inline and block.

Inline comments start with the # character and continue until the end of the line:

# On a separate line
class Foo # or at the end of the line
  # can be indented
  def bar
  end
end

Block comments start with =begin and end with =end. Each should be on a separate line.

=begin
This is
commented out
=end
class Foo
end

=begin and =end can not be indented, so this is a syntax error:

class Foo
  =begin
  Will not work
  =end
end

Comments as documentation

The Ruby standard library includes the RDoc tool for generating documentation from code. RDoc format is “unobtrusive” (plain text) documentation. Ruby gem YARD is also frequently used to generate documentation, providing a more strict format allowing rendering of “tags” (param types, return type, examples and so on).