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module_function_usage

✨ Converting Module Methods to Both Instance and Module Functions​

module_function lets you reuse methods internally as private instance methods and externally as module (or class) methods. It’s helpful for utility modules that need consistent behavior across contexts.

module Formatter
  module_function

  def truncate(text, length)
    text[0...length] + '...'
  end
end

# As module method
e = Formatter.truncate("Hello, World!", 5)
# => "Hello..."

# As private instance method
class Post
  include Formatter

  def summary
    truncate(content, 10)
  end
end