Rails - Jul 2007 - efficient, "Rails Way" method of doing a somewhat complex find

I''m still a newb w/r/t rails and ruby, so this may be obvious, but I
havent found an answer in my searching yet...

I have a visibility attribute on a Story model that says some of the
objects can only be seen by "friends" and some just by
"family".

I also have a Contacts model where each object has an attribute to
mark them as a Friend or Family for a given User.

My User model hasMany Stories and hasMany Contacts.

Maybe you see where this is going...

When a user is logged in, I want to show them only the Stories that
should be visible to them as determined by one of the following two
logical matches:

a) the Story is only visible to Friends and the user is in the Story
owner''s Friends list
b) the Story is only visible to Family and the user is in the Story
owner''s Family list

What I''m looking for is the best way to do this by doing it "the
Rails
Way" and being as efficient as possible.

I was starting to approach it like this:

1) get the list of users for which the current user is in their
Friends list

2) get the list of users for which the current user is in their Family
list

3) find and show Stories where visibility = Story::VISIBLITY_FRIENDS
and current_user is in list 1 OR where visibility Story::VISIBLITY_FAMILY and
current_user is in list 2

...but this seems clumsy and maybe a performance hog... also I''m not
sure yet how to do a SQL IN clause in Rails.

Anyone have suggestions for a better approach?

And could someone show me how to do that IN clause in a find method
(I''ve searched and haven''t found it yet)? Guess I could do a
find_by_sql call...

Thanks in advance.


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On 7/20/07, lunaclaire <szagerman-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:
>
> I''m still a newb w/r/t rails and ruby, so this may be obvious, but
I
> havent found an answer in my searching yet...
>
Here is the most concise solution I could come up with based on your
description and off the "top of my head". I didn''t test this
code, so
I don''t guarantee it 100%.

Whenever someone is looking at a page of another user''s stories, you
have the two IDs with which to find a Contact instance. From that
contact instance you can simply call .stories...

Have fun! (And as you see an IN clause wasn''t even necessary.)

# == Schema Information
# Table name: users
#  id                  :integer(11)   not null, primary key
#  name                :string(255)
class User < ActiveRecord::Base
  has_many :stories
end

# == Schema Information
# Table name: contacts
#  id                  :integer(11)   not null, primary key
#  from_id             :integer(11)
#  to_id               :integer(11)
#  family              :boolean
#  friend              :boolean
class Contact < ActiveRecord::Base
  belongs_to :from_user, :class_name => "User", :foreign_key =>
"from_id"
  belongs_to :to_user,   :class_name => "User", :foreign_key =>
"to_id"

  def stories
    conditions = {}
    conditions[:family_only] = false unless to_user.family?
    conditions[:friend_only] = false unless to_user.friend?
    from_user.stories.find(:all, :conditions => conditions)
  end
end

# == Schema Information
# Table name: stories
#  id                  :integer(11)   not null, primary key
#  user_id             :integer(11)
#  family_only         :boolean
#  friend_only         :boolean
class Story < ActiveRecord::Base
  belongs_to :user
end

Cheers and good luck,
Obie

-- 
Pre-order my book The Rails Way
http://www.amazon.com/dp/0321445619

blog: http://jroller.com/obie/

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