Ruby how to reset class methods

Question

Using module_eval, my code allows me to dynamically create and add new methods to a class based on input parameters. See this post for an example http://stackoverflow.com/questions/2039826/ruby-classeval-and-yield

Now my question is how do I reset the class back to its original methods? Is there a simple method I can use to reset a class back to it's original state? The reason for this is that once new methods are added to the class, they persists and I need to be get rid of them if I create a new object with a different set of methods.

Also I must apologize if this question doesn't quite make sense, I've been up for 24 hours and probably needed to get some rest to think clearly. If this is not clear, I can provide an example. Thanks for your help in advance.

Answer 1

I would take one of two tacks:

• either move the original class methods to a module, which you can re-include later
• or use module_eval on a subclass of the original class, and just get a new subclass when you want to reset.

The second's a little easier to do:

 subklass = Class.new(MyAwesomeClass)
 subklass.module_eval #...

 # ok, I'm done, I want to reset
 subklass = Class.new(MyAwesomeClass)

Answer 2

Edit: Added complete solution

If you keep a list of the methods added in your earlier post, you can use remove_method to remove these methods with something like:

class MyTest
  @@methods_list = []

  def self.show_methods
    @@methods_list
  end

  def self.reset_methods
    @@methods_list.each do |method|
      remove_method(method)
    end
    @@methods_list = []
  end

  def self.add_methods
    define_method("method1")  { puts "This is method1" }
    define_method("method2")  { puts "This is method2" }
    true
  end

  def self.method_added(method_name)
    @@methods_list << method_name.to_s
    puts "Added: " + method_name.to_s + ", list: " + @@methods_list.inspect
  end
end

Now you can try out the following:

>> require 'mytest.rb'
>> t = MyTest.new # => #<MyTest:0x2b1e293247f0>
>> MyTest.add_methods
Added: method1, list: ["method1"]
Added: method2, list: ["method1", "method2"]
>> t.method1 # Method is available:
This is method1
>> MyTest.reset_methods
>> t.method1 # Method is undefined now, so we'd expect an error
NoMethodError: undefined method `method1' for #<MyTest:0x2b1e293247f0>
    from (irb):6