Show how class methods can be wrapped to intercept and manage their return values without code changes in their clients.

method_wrapper.rb

# show how class methods can be wrapped to intercept and manage their return values without code changes in their clients.

class MyClass
  class << self
    def method_one
      "result from method one"
    end

    def method_two
      "result from method two"
    end
  end
end

module Wrapper
  def report_return_value(klass, method_name)
    original_method = klass.singleton_method(method_name)
    define_singleton_method(method_name) do |*args|
      result = original_method.call(*args)
      puts "Return value of #{method_name}: #{result}"
      result
    end
  end

  def wrap_them_all
    report_return_value(MyClass, :method_one)
    report_return_value(MyClass, :method_two)
  end
end

MyClass.extend Wrapper

MyClass.wrap_them_all

MyClass.method_one
MyClass.method_two

This is what the output looks like:

$ ruby method_wrapper.rb
Return value of method_one: result from method one
Return value of method_two: result from method two