I have two tables with a join table between them:
Parent: Pages
Child: Things
Join: Grids
In my models they are set up with a many to many relationship (has_many through):
class Page < ActiveRecord::Base
belongs_to :books
has_many :grids
has_many :things, :through => :grids
end
class Thing < ActiveRecord::Base
has_many :grids
has_many :pages, :through => :grids
end
class Grid < ActiveRecord::Base
belongs_to :page
belongs_to :thing
end
Now I want to be able to sort "things" using an ordering id from grid, called number, how can I do that ?
Thanks!
you need the ":include(s)" option in your find method, and then "order_by()" ...
you would use something like this:
Thing.where(...some condition or all..., :include => :grid ).order_by(grid.number)
See:
http://guides.rubyonrails.org/active_record_querying.html
http://m.onkey.org/active-record-query-interface
http://api.rubyonrails.org/classes/ActiveRecord/Associations/ClassMethods.html
Related
I am looking for a way to query a model based on children in a has_many through association.
I have 3 models:
class Conversation < ActiveRecord::Base
has_many :conversations_participants
has_many :participants, through: :conversations_participants
end
class ConversationsParticipant < ActiveRecord::Base
belongs_to :conversation
belongs_to :participant, class_name: 'User'
end
class User < ActiveRecord::Base
has_many :conversations_participants
has_many :conversations, through: :conversations_participants
end
I need to find conversations where participants matches an array of ids.
This is what i have at the moment (not working):
Conversation.includes(:participants).where(participants: params[:participants])
Sounds like you just want the conversations, if so you can joins.
Conversation.joins(:participants).where(:users => { :id => params[:participants] } )
Otherwise, if you want to eager load the participants, use includes
Conversation.includes(:participants).where(:users => { :id => params[:participants] } )
You can pass an array like this:
Conversation.includes(:participants).where(:id => params[:participants])
Assuming that params[:participants] is an array.
Conversation.includes(:participants).where( 'conversation_participants.participant_id' => params[:participants])
assuming that participant_id is the foreign key of participants in the conversation_participants table
The image shows part of my data model. I would like to fetch all items that are associated with a user (through organizations and items_group). How should I change the models and write this query in the controller? Using :through => organizations I can get all items_groups but I don't how to include one more relation to query related items.
class User < ActiveRecord::Base
has_and_belongs_to_many :organizations
has_many :items_groups, :through => :organizations
end
class Organization < ActiveRecord::Base
has_and_belongs_to_many :users
has_and_belongs_to_many :items_groups
has_many :items, :through => :items_groups
end
class ItemsGroup < ActiveRecord::Base
has_many :items, :inverse_of => :items_group
has_and_belongs_to_many :organizations
has_many :users, :through => :organizations
end
I think you might have to do it back-to-front and find items joined back to your user.
You could define method like this in your User class:
def items
Item.joins(:items_group => {:organizations => :users}).where("users.id" => self.id).select("distinct items.*")
end
The items it returns will be read-only because of the explicit select but I think you'll want that to avoid returning individual items more than once.
If you set in your models the relationships this should work:
users.organizations.item_groups.items
Though for it to work your models should contain this:
class User < ActiveRecord::Base
has_many :organizations, :through => :organization_users
end
class Organization < ActiveRecord::Base
has_many :item_groups, :through => :items_groups_organizations
end
class ItemsGroup < ActiveRecord::Base
belongs_to :item
end
Hope it works for you!
I have three models
class Collection < ActiveRecord::Base
has_many :presentations
has_many :galleries, :through => :presentations
end
class Gallery < ActiveRecord::Base
has_many :presentations
has_many :collections, :through => :presentations
end
class Presentation < ActiveRecord::Base
belongs_to :collection
belongs_to :gallery
end
How do I get all the collections that do not belong to a given gallery?
My SQL knowledge is only rudimentary. I also want to let Rails (2.3) do the work without using explicitly a SQL expression.
Out of the box, you technically have to write some SQL (where clause)...
gallery_to_exclude = Gallery.first
Collection.find(:all,
:include => :presentations,
:conditions => ['presentations.gallery_id IS NULL OR presentations.gallery_id != ?',
gallery_to_exclude.id])
If you want to use Searchlogic, you can avoid this, though:
Collection.presentations_gallery_id_is_not(gallery_to_exclude.id).all
I've found an old plugin called acts_as_habtm_list - but it's for Rails 1.0.0.
Is this functionality built in acts_as_list now? I can't seem to find any information on it.
Basically, I have an artists_events table - no model. The relationship is handled through those two models specifying :has_and_belongs_to_many
How can I specify order in this situation?
I'm assuming that you have two models - Artist and Event.
You want to have an habtm relationship between them and you want to be able to define an order of events for each artist.
Here's my solution. I'm writing this code from my head, but similar solution works in my case. I'm pretty sure there is a room for improvement.
I'm using rails acts_as_list plugin.
That's how I would define models:
class Artist < ActiveRecord::Base
has_many :artist_events
has_many :events, :through => :artist_events, :order => 'artist_events.position'
end
class Event < ActiveRecord::Base
has_many :artist_events
has_many :artists, :through => :artist_events, :order => 'artist_events.position'
end
class ArtistEvent < ActiveRecord::Base
default_scope :order => 'position'
belongs_to :artist
belongs_to :event
acts_as_list :scope => :artist
end
As you see you need an additional model ArtistEvent, joining the other two. The artist_events table should have two foreign ids and additional column - position.
Now you can use acts_as_list methods (on ArtistEvent model, unfortunately) but something like
Artist.find(:id).events
should give you a list of events belonging to specific artist in correct order.
Additional update for the accepted answer: for Rails 4 and Rails 5:
has_many :events, -> { order 'artist_events.position ASC' }, through: :artist_events
has_many :artists, -> { order 'artist_events.position ASC' }, through: :artist_events
I trying with self-referencing like that
class Product < ActiveRecord::Base
has_many :cross_sales
has_many :cross_sales_products, :through => :cross_sales, :order => 'cross_sales.position'
end
class CrossSale < ActiveRecord::Base
default_scope :order => 'cross_sales.position'
belongs_to :product
belongs_to :cross_sales_product, :class_name => "Product"
acts_as_list :scope => :product
end
create_table :cross_sales, :force => true, :id => false do |t|
t.integer :product_id, :cross_sales_product_id, :position
end
But the field cross_sales.position is never updated ...
An idea ?
Update: Ok the field 'id' it's necessary in the case of additional model with has_many :through option. It's work well now
In the accepted answer, note that :order => 'artist_events.position' is referencing the table artist_events and not the model.
I ran into this minor hiccup when moving from a habtm association to has_many :through.
Consider the following models:
class Artist < ActiveRecord::Base
has_many :artist_events
has_many :events, :through => :artist_events
end
class Event < ActiveRecord::Base
has_many :artist_events
has_many :artists, :through => :artist_events, :order => 'artist_events.position'
end
class ArtistEvent < ActiveRecord::Base
default_scope :order => 'position'
belongs_to :artist
belongs_to :event
acts_as_list :scope => :artist
end
Is is possible to use ActiveScaffold to administer this type of relationship? The ArtistEvent model exists to define a hbtm relationship with additional attribute of position.
Thanks!
Jonathan
yes. after all, ArtistEvent is yet another model - and active scaffold can operate on it as long as you have routes and controllers on the join model.