Sod will_paginate library

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  Chris Wanstrath July 26th, 2007 @ 07:31 PM

  • State changed from “new” to “open”
  • Assigned user changed from “Chris Wanstrath” to “Mislav”

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  Andreas Neuhaus July 26th, 2007 @ 07:31 PM

  I wrote up a more detailed description of this problem in a posting in my Blog

• 

  Mislav July 26th, 2007 @ 07:31 PM

  • State changed from “open” to “invalid”

  So, you would like this:

  class User < AR::Base
    def self.find_all_special(options = {})
      with_scope(:find => { :conditions => "...", :order => "..." }) do
        find(:all, options)
      end
    end
  
    def self.count_special(options = {})
      with_scope(:find => { :conditions => "...", :order => "..." }) do
        count(options)
      end
    end
  end
  
  User.paginate_special(:page => 1)
  

  Right?

  But don't you see that you didn't manage to stay DRY anyway? It is because you're using with_scope totally wrong. Isn't this much better?

  class User < AR::Base
    def self.paginate_special(options)
      with_scope(:find => { :conditions => "...", :order => "..." }) do
        paginate(options)
      end
    end
  end
  
  User.paginate_special(:page => 1)
  

  Or even this

  class Developer < User
    def self.with_poor_ones(&block)
      with_scope :find => { :conditions => ['salary <= ?', 80000], :order => 'salary' } do
        yield
      end
    end
  end
  
  Developer.with_poor_ones do
    Developer.paginate :page => 1
  end
  

  But this last example may be frowned upon by Rails purists. Better stick with the middle example.

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  Andreas Neuhaus July 26th, 2007 @ 07:31 PM

  Thanks, Mislav. Indeed using a custom paginate method would solve the problem - however, only if you need just the paginate method. If you also need the non-paginated custom finder somewhere, you'd become non-DRY again (more on that in my reply to your comment post in my blog).

  Another idea came into my mind: will_paginate is easy to use, because it's unobstrusive. You write models like before and get pagination on top by installing will_paginate. It would be nice if that could also be possible with custom finders. It almost works already - except that the wrong count of total records is retrieved. To get the right count, all that would be required, is to let the custom finder build the SQL conditions like before and use it with count ('select count(*)') instead of find ('select *'). I'm not sure how AR works and if this is even possible without chaning AR itself, but that would be a great will_paginate feature.

• 

  Mislav July 26th, 2007 @ 07:31 PM

  At first I thought it was a good feature, yes. But then I though about

  how this custom counters would be implemented, and I realized users

  would have to duplicate logic in finders and corresponding counters.

  So, will_paginate would support bad coding practice then.

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  Adam Cohen August 23rd, 2007 @ 11:33 PM

  I echo your concerns Zargony, I'd love to see support for custom complex finders as well. Is this a possibility in the future Mislav?

• 

  Mislav August 24th, 2007 @ 12:14 AM

  Will Paginate now supports the scope_out plugin. Continue the discussion on the blog...