From: Simen Edvardsen <toalett@...>
Date: 2006-12-16T23:46:26+09:00
Subject: Re: calling child from parent

On 12/16/06, dc <lister@pikkle.com> wrote:
> hi -
>
> i understand super passes method calls up to the parent.
>
> is there a way to call down to the child instance, to a different method?
>
> I realize i could pass a function block up to super, and then use
> yield to call back to the child, but i want to hide this complexity
> from my child classes.
>
> the setup is something like this:
>
> class Webserver < HTTPServlet::AbstractServlet
>     def do_GET(request, response)
>        // here i want to hand off to the instance child servlet to
> handle the response
>        child.render()
>    end
> end
>

Just (re)define render in the child. Example:

$ irb
irb(main):001:0> class Webserver
irb(main):002:1>   def get
irb(main):003:2>     puts "In superclass"
irb(main):004:2>     render
irb(main):005:2>   end
irb(main):006:1>   def render
irb(main):007:2>     puts "In superclass#render"
irb(main):008:2>   end
irb(main):009:1> end
=> nil
irb(main):010:0> class Servlet < Webserver
irb(main):011:1>   def render
irb(main):012:2>     puts "In subclass#render"
irb(main):013:2>   end
irb(main):014:1> end
=> nil
irb(main):015:0> Servlet.new.get
In superclass
In subclass#render

But remember, a superclass doesn't know about its subclasses.

>
> class Servlet1 < Webserver
>    def render
>      // do some stuff
>   end
> end
>
> etc for other servlets.
>
> I guess the other way is to instantiate the right child servlet in the
> webserver, but this means i dont get access to super methods...
>
> tx,
>
> /dc
> -------------------------------------------
>       David "DC" Collier
> mailto:dc@pikkle.com
>       +81 (0)80 6521 9559
>       skype: callto://d3ntaku
> -------------------------------------------
>       Pikkle 株式会社
>       http://www.pikkle.com
> -------------------------------------------
>
>


-- 
- Simen