From: Rajinder Yadav <devguy.ca@...>
Date: 2009-12-15T20:12:40+09:00
Subject: Re: meta-programming

Jes�s Gabriel y Gal�n wrote:
> On Tue, Dec 15, 2009 at 9:32 AM, Rajinder Yadav <devguy.ca@gmail.com> wrote:
>> I am just starting to expand my Ruby knowledge into the area of
>> meta-programming.
>>
>> I want to be able to create a class dynamically. Lets call it, class Person,
>> and then I want to add methods to it dynamically.
>>
>> From a static point I have managed to compile the following example:
>>
>> class Person
>>   def self.extend_me
>>   class_eval "def greet; puts 'hello'; end"
>>   instance_eval "def name; puts 'Person'; end"
>>   end
>> end
>>
>> Person.extend_me
>>
>> Person.respond_to? :greet
>> Person.respond_to? :name
>>
>> puts Person.name
>> p = Person.new
>> puts p.greet
>>
>>
>> How would I declared a, 'class Person' dynamically and then add methods and
>> attributes to it? Can someone point me to good documentation on this or show
>> me some simple code example?
> 
> If you want to define the class dynamically, take a look at Class.new.
> This creates an anonymous class that you can assign to a constant
> directly or with const_set.
> To define methods I would use define_method. Adding attributes is done
> adding methods that set and get the attributes:
> 
> irb(main):042:0> C = Class.new do
> irb(main):043:1* def self.add_method(name, &blk)
> irb(main):044:2> define_method(name, &blk)
> irb(main):045:2> end
> irb(main):046:1> end
> => C
> 
> irb(main):051:0> C.add_method(:name) {@name}
> => #<Proc:0xb7cb9de8@(irb):51>
> irb(main):052:0> C.add_method(:name=) {|value| @name = value}
> => #<Proc:0xb7cb3bf0@(irb):52>
> irb(main):053:0> c = C.new
> => #<C:0xb7cb16d4>
> irb(main):054:0> c.name=3
> => 3
> irb(main):055:0> c.name
> => 3
> 
> Hope this helps,
> 
> Jesus.
> 
> 

Hi Jesus, yes it does help and you answered the next question I was 
about to ask about adding variables after reading Brian's reply.

-- 
Kind Regards,
Rajinder Yadav

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