Re: Dynamically changing class methods

On Fri, 12 Aug 2005, henrikbrink wrote:

Hello!

Im making an application that loads and uses the methods of a class
dynamically. The class can then be altered while the application is
running, and the application loads the file containing the class every
time it is needed.

The strange thing is: It works fine when i add a method to the class.
The new method shows up. But if i remove a method, it acts as if it was
still there. How can that be?

Here's the code used to get the methods:

   load "#{file}.rb"
   myclass = Object.const_get "MyClass"
   myclass_inst = myclass.new
   methods = myclass_inst.methods

If I am not clear enough, please ask.

Regards, Henrik 

because:

  harp:~ > irb
  irb(main):001:0> class Foo;def foo;end;end

  irb(main):002:0> p Foo::instance_methods - Object::instance_methods
  ["foo"]

  irb(main):003:0> class Foo;def bar;end;end

  irb(main):004:0> p Foo::instance_methods - Object::instance_methods
  ["bar", "foo"]


opening up a class, even in a file that's loaded, can only add or modify
methods using 'def'.  there is a mechanism to delete methods but it must be
explicit.

for dynamically loading classes try this:


    jib:~ > cat b.rb

      require 'dynaload'
      loaded = Dynaload::dynaload 'a.rb'
      loaded.classes.each do |klass, attributes|
        p [klass, attributes]
        p klass.instance_methods - Object.instance_methods
      end


    jib:~ > cat a.rb

      require 'dynaload'
      class Foo
        def foo
        end
      end
      Dynaload::export Foo, 'some attribute' => 42


    jib:~ > ruby b.rb

      [#<Module:0xb75cded8>::Foo, {"some attribute"=>42}]
      ["foo"]


    jib:~ > cat a.rb

      require 'dynaload'
      class Foo
        def bar
        end
      end
      Dynaload::export Foo, 'some attribute' => 42


    jib:~ > ruby b.rb

      [#<Module:0xb75cbed8>::Foo, {"some attribute"=>42}]
      ["bar"]


http://raa.ruby-lang.org/project/dynaload/
http://www.codeforpeople.com/lib/ruby/dynaload/

hth.

-a
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.

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