ActiveRecord query assistance
i need a little help with a AR query. This is how my models look like:
class User < AR:B
has_many :publications
end
class Publication < AR:B
belongs_to :user
belongs_to :category
end
class Category < AR:B
has_many :publications
end
Now let's say I want to iterate over all existing categories and either display the user's publications, or display something like "#{current_user.name} has no publications in this category".
class PublicationsController < AC:B
def index
@categories = Category.find(:all, :include => :publications, :conditions => { 'publications.user_id' => current_user })
end
end
This gives me all Categories the user a开发者_如何转开发ctually has publications, but lacks the "empty" ones.
Any suggestions? :-)
This gives you all the Category objects:
@categories = Category.all
Then, if you declare has_many :through associations you can do something like the following:
@categories.each do |category|
if category.users.include?(current_user)
# User has publications
publications = category.publications.select { |pub| pub.user == current_user }
else
# User has no publications
end
end
(has-many-through declarations:
class User < AR:B
has_many :publications
has_many :categories, :through => :publication
end
class Publication < AR:B
belongs_to :user
belongs_to :category
end
class Category < AR:B
has_many :publications
has_many :users, :through => :publication
end
... warning: drycode)
There's probably an neater way to do this using named scopes though.
You might be able to just modify the find call:
@categories = Category.find(:all, :include => :publications, :conditions => [ 'publications.user_id=? OR publications.user_id IS NULL', current_user ])
Notice that we use the Array variant here rather than the Hash variant, since the example in the documentation implies this is the correct usage.
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