From: Rein Henrichs <reinh@...>
Date: 2010-06-15T02:20:06+09:00
Subject: Re: Metaprograming

On 2010-06-14 01:22:40 -0700, Jes�s Gabriel y Gal�n said:

> On Mon, Jun 14, 2010 at 7:23 AM, Sateesh Kambhamapati
> <sateesh.mca09@gmail.com> wrote:
>> Jes�s Gabriel y Gal�n wrote:
>>> On Thu, Jun 10, 2010 at 11:53 AM, Sateesh Kambhamapati
>>> <sateesh.mca09@gmail.com> wrote:
>>>> end
>>>> end
>>>> f=flower.new
>>>> f.rose-------------------->It gives me rose
>>>> but now f.jasmine------------------->It calls method_missing
>>>> but i want it comes to my class "Flower"
>>> 
>>> I'm not sure if I understand you correctly, but if you want those
>>> method missing calls, to be called on the Flower class, you can do
>>> this:
>>> 
>>> irb(main):001:0> class Flower
>>> irb(main):002:1> def self.jasmine
>>> irb(main):003:2> "jasmine"
>>> irb(main):004:2> end
>>> irb(main):005:1> def method_missing meth, *args, &blk
>>> irb(main):006:2> self.class.send meth, *args, &blk
>>> irb(main):007:2> end
>>> irb(main):008:1> end
>>> => nil
>>> irb(main):016:0> Flower.new.jasmine
>>> => "jasmine"
>>> 
>>>> So i Want to know which methods are invoked by my "Flower" object
>>> 
>>> I don't understand this question.
>>> 
>>> Jesus.
>> 
>> Thanks for reply
>> i would like to know which methods are called by class object i.e
>> class Flower
>> � � def jasmine
>> � � puts "iam jasmine"
>> � end
>> � � �def rose
>> � � �puts "iam rose"
>> �end
>> end
>> 
>> flowerlist=Flower.new #----->Creating instance for flower
>> flowerlist.jasmine �#------->"gives output as "iam jasmine"
>> flowerlist.rose �# =======> "gives output as "i am rose"
>> flowerlist.lotus � #------->"Shows No Method Error"
>> 
>> Question : --> My Question is i would like to know which methods are
>> called by object i.e flowerlist �in the class Flower
>> 
>> if i already know those methods then
>> suppose if i have not define some method then i will define it
>> dynamically example here is "lotus"
>> 
>> i think u understand my question
> 
> As I understand the question now, I think the answer from Phrogz is
> spot on. You need to use the method_missing method, which will catch
> any call to a method you haven't defined:
> 
> class Flower
>   def jasmine
>     puts "iam jasmine"
>   end
>   def rose
>     puts "iam rose"
>   end
> 
>   def method_missing meth, *args, &blk
>     puts "method #{meth} called, but not defined"
>   end
> end
> 
> flowerlist=Flower.new #----->Creating instance for flower
> flowerlist.jasmine  #------->"gives output as "iam jasmine"
> flowerlist.rose  # =======> "gives output as "i am rose"
> flowerlist.lotus   #=> "method lotus called, but not defined"
> 
> So, now you know where you have a place to do whatever you want to do
> with a call to a method that doesn't exist. For example, if you want
> to dynamically create a method that returns its name as a string, you
> can do:
> 
>   def method_missing method, *args, &blk
>     self.class.send(:define_method, method) do
>       method.to_s
>     end
>     send(method)
>   end
> 
> This will dynamically define (and call) a method that returns its name
> as a string. So if you add that to the Flower class:
> 
> class Flower
>   def method_missing method, *args, &blk
>     self.class.send(:define_method, method) do
>       method.to_s
>     end
>     send(method)
>   end
> end
> 
> f = Flower.new
> f.lotus #=> "lotus"
> f.rose #=> "rose"
> 
> and so on. In any case, I recommend looking at Phrogz's answer,
> because it's a nice little utility to automatically define method that
> do different things depending the the name patterns.
> 
> Regards,
> 
> Jesus.

My goodness. Has anyone asked why such metaprogramming might be 
necessary? I don't even understand the question, let enough to the 
extent that I would feel confident in suggesting such drastic measures 
as the solution.

Metaprogramming is not a universal hammer. Even if it were, you 
wouldn't want everything to be a nail.

-- 
Rein Henrichs
http://puppetlabs.com
http://reinh.com