Paginate custom finders

#66

I'm having problems using will_paginate with a custom finder method in my models:

@@@ Ruby class User < AR::Base
def find_all_special (options = {}) with_scope(:find => {:conditions => "...", :order => "..." }) do find(:all, options) end end end


Retrieving records by using @users=User.paginate_special(...) does work, because using paginate_xyz calls find_all_xyz and adds offset/limit options to retrieve the records. However the paginate method does not retrieve the correct record count. It uses the count method but isn't able to apply the scope that could be applied in a custom finder method. Therefore the will_paginate helper displays more pages than actually exist.




Because I want to keep the search conditions within my model classes, I solved this problem by adding a count_special method which returns the number of records by using "count" within the proper scope. However now I have to specify :total_entries => User.count_special whenever using paginate_special; which isn't very DRY (and I tend to forget to add this option sometimes)




It would be nice if will_paginate would automatically use a custom counter method if such one exists (like automatically using count_special if paginate_special is used).




Or does somebody else maybe know a better way to paginate cutstom finder methods in a DRY way?

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

Activity

Chris Wanstrath
- State changed from new to open
- Assigned user changed from Chris Wanstrath to Mislav
July 26th, 2007 @ 07:31 PM
Andreas Neuhaus
I wrote up a more detailed description of this problem in a posting in my Blog

July 26th, 2007 @ 07:31 PM

Mislav

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.

July 26th, 2007 @ 07:31 PM

Andreas Neuhaus
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.

July 26th, 2007 @ 07:31 PM
Mislav
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.

July 26th, 2007 @ 07:31 PM
Adam Cohen
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?

August 23rd, 2007 @ 11:33 PM
Mislav
Will Paginate now supports the scope_out plugin. Continue the discussion on the blog...

August 24th, 2007 @ 12:14 AM

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