Thanks a lot Christophe. This was very helpfull.
Thank you.
On Apr 7, 3:12 am, Christophe Porteneuve <[EMAIL PROTECTED]> wrote:
> Divya Khullar a écrit :
>
> > Hello I am new to rails. I was going through the gallery example in
> > Ajax on Rails book and i came accorss this code. It beats me what this
> > means. Please can one of you Rails Guru help me
>
> That's meta-programming: this code build fragments of Ruby code that
> then get eval'd in the context of the current class. In short, it
> synthesizes new methods for the current class, on the fly.
>
> > %w(full thumb medium).each do |size|
>
> OK, so we'll create code fragments for three methods: 'full', 'thumb'
> and 'medium' (%w produces a string array from its argument).
>
> > class_eval <<-END
>
> Everything else until we meet 'END,' possibly indented, is a string
> literal that will end up being passed to class_eval.
>
> > def #{size}
>
> This code defines a method named after the current value of /size/ (e.g.
> 'full').
>
> > find_photo
> > send_data @photo.#{size}, :filename =>
> > "[EMAIL PROTECTED]", :type => 'image/jpeg', :disposition =>
> > 'inline'
>
> The method will simply grab the picture object, and send the binary
> contents of the proper field of it (@photo is an object found by
> find_photo, and #{size} will be expanded in your Ruby code string to the
> current value of size, as before on the /def/ line.
>
> > end
> > caches_page :#{size}
>
> Let's cache this result for performance
>
> > END
>
> End of the Ruby code string: class_eval gets called and turns this Ruby
> into reality.
>
> > end
>
> End of the each iteration. You just generated three new methods!
>
> 'HTH
>
> --
> Christophe Porteneuve a.k.a. TDD
> "[They] did not know it was impossible, so they did it." --Mark Twain
> Email: [EMAIL PROTECTED]
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