I've got a question about associations in Rails 2.3.11
I have two models:
Activities
Organisations
they have a has_and_belongs_to_many relationship. But they also have an important and per-activity-organisation relationship type. They are connected together via the activities_organisations table, which has three columns:
activity_id
organisation_id
rel_type
The rel_type can be set as 1 (funding), 2 (extending) or 3 (implementing).
The association works fine and I can call #activity.organisations or #organisation.activities. But I'd also like to call this depending on the rel_type - so that I can for example call only an activity's implementing organisation (where rel_type == 3)
At the moment I have this (on the Organisations / index view), but I think there must be a nicer way?
<%
#conditions = {}
#conditions[:organisation_id] = organisation.id
#reltype = ActivitiesOrganisation.all(:conditions=>#conditions, :group=>:rel_type)%>
<td><% #reltype.each do |r| %><%= r.rel_type %><% end %></td>
</tr>
<% end %>
<% end %>
I found this but I got stuck trying to include it in my models, and I'm not sure how much of it applies.
Would be extremely grateful for any help!
Thanks,
Mark
Update:
Thanks to #ghoppe in the comments, I realised I was being a bit of an idiot... This is my code now:
Activity Model
class Activity < ActiveRecord::Base
has_many :activity_organisations
has_many :funding_activity_organisations, :class_name => "ActivitiesOrganisation",
:conditions => {:rel_type => 1}
has_many :extending_activity_organisations, :class_name => "ActivitiesOrganisation",
:conditions => {:rel_type => 2}
has_many :implementing_activity_organisations, :class_name => "ActivitiesOrganisation",
:conditions => {:rel_type => 3}
has_many :organisations, :through => :activity_organisations
has_many :funding_organisations, :through => :funding_activity_organisations, :source => :organisation
has_many :extending_organisations,:through => :extending_activity_organisations,:source => :organisation
has_many :implementing_organisations,:through => :implementing_activity_organisations,:source => :organisation
end
ActivitiesOrganisation Model
class ActivitiesOrganisation < ActiveRecord::Base
belongs_to :activity
belongs_to :organisation
end
Thanks!
Related
This is a rather simple Rails 4 situation. Model Intranet has_many activities. Activities exists with sufficient records for several intranets. Current_intranet.activities.size returns 69 records. However, whenever I try to access any of the records, I receive "output error: <ArgumentError: wrong number of arguments (1 for 0)" even though I'm not passing any arguments. All of the following fail with that error.
Current_intranet.activities.first
Activity.where(intranet_id: 1).first
Activity.where(:intranet_id => 1).first
Activity.where{intranet_id.eq 1}.first
All of the above with [0] instead of first
There is no problem with any other models
I'd appreciate any suggestions. Thanks in advance.
There are no defined scopes. The code is:
class Activity < ActiveRecord::Base
acts_as_capitalized
# activities created during intranet creation.
DEFAULT_ACTIVITIES = { 'Document Preparation' => 'general income', 'No Charge' => 'general income'}
# static activity names that can not be deleted.
STATIC_ACTIVITY_NAMES = [ 'Document Preparation','No Charge']
before_destroy :check_if_used
before_destroy :cannot_delete_static_activities
belongs_to :created_by_user, :class_name => "User", :foreign_key => "created_by"
belongs_to :updated_by_user, :class_name => "User", :foreign_key => "updated_by"
belongs_to :intranet
belongs_to :chart_of_account
has_many :activity_rates, :dependent => :destroy
has_many :event_type
has_many :billings do
def find_by_name(name)
(find :all, :conditions => ["activity.name = ?",name])
end
end
has_many :document_templates, :foreign_key => "billing_activity_id"
validates_presence_of :intranet_id, :name, :chart_of_account_id
validates_uniqueness_of :name, :scope => :intranet_id
I have this relation in my Product model:
has_many :features, :class_name => 'ProductFeature', :source => :product_feature, :include => :feature
So I can do Product.features
which works fine. But I want to be able to filter that by fields in the feature table, when and if necessary. For example in pseudo code:
find all product features where feature is comparable
compare is a bool field on the feature.
I have been trying for 2 hours solid and cannot figure it out (without writing a new query completely). I can't figure out how to access the feature table's fields from the Product.features relation, as it seems it can only filter on product_features fields.
This is what I have come up with so far:
def features_compare
features.feature.where(:compare => true)
end
But it just says feature is not a valid method, which I understand.
Edit
I have updated my model so the relationships are clearer:
product.rb:
class Product < ActiveRecord::Base
belongs_to :company
belongs_to :insurance_type
has_many :product_features
has_many :reviews
attr_accessible :description, :name, :company
end
product_feature.rb:
class ProductFeature < ActiveRecord::Base
belongs_to :product
belongs_to :feature
delegate :name, :to => :feature
attr_accessible :value
end
feature.rb
class Feature < ActiveRecord::Base
attr_accessible :name, :compare
end
I want to be able to query the product_features that belong to a product and feature where Feature.compare is true. Something like this:
product.rb
def features_compare
product_features.where(:compare => true)
end
This throws an error because compare in in the Feature model, not ProductFeature. I have tried the following in product_feature.rb:
delegate :compare, :to => :feature
but I didn't help.
I will adding a bounty to this in a few hours so please please help me!
find all product features where feature is comparable is just
ProductFeature.joins(:feature).where(:feature => {:compare => true})
You can make that a bit more reusable by introducing a scope:
#in product_feature.rb
scope :with_feature_like, lambda do |filter|
joins(:feature).where(:feature => filter)
end
#elsewhere
ProductFeature.with_feature_like(:compare => true)
#all the product features of a certain product with at comparable features
some_product.product_features.with_feature_like(:compare => true)
Finally, if you want all products with product features with comparable features, you want something like:
Product.joins(:product_features => :feature).where(:feature => {:compare => true})
which of course you can also turn into a scope on Product.
This seems like a has_many :through relationship. Try changing this:
has_many :features, :class_name => 'ProductFeature', :source => :product_feature, :include => :feature
to this:
has_many :product_features
has_many :features, :through => :product_features
As long as your ProductFeature model has this:
belongs_to :product
belongs_to :feature
And you have the appropriate columns on product_features (product_id, feature_id), then you should be able to access that product's features and all the attributes on both Product and ProductFeature.
See here:
http://guides.rubyonrails.org/association_basics.html#the-has_many-through-association
EDIT: Here's how to filter by feature fields.
Product.joins(:features).where(:features => {:name => "Size"})
#product.each |p| { p.features.where(:comparable => true) } is probably your best bet here, but I'm open to being enlightened.
Similar to this question, how do I set a property on the join model just before save in this context?
class Post < ActiveRecord::Base
has_many :post_assets
has_many :assets, :through => :post_assets
has_many :featured_images, :through => :post_assets, :class_name => "Asset", :source => :asset, :conditions => ['post_assets.context = ?', "featured"]
end
class PostAssets < ActiveRecord::Base
belongs_to :post
belongs_to :asset
# context is so we know the scope or role
# the join plays
validates_presences_of :context
end
class Asset < ActiveRecord::Base
has_many :post_assets
has_many :posts, :through => :post_assets
end
I just want to be able to do this:
#post = Post.create!(:title => "A Post")
#post.featured_images << Asset.create!(:title => "An Asset")
# ...
#post = Post.first
#featured = #post.featured_images.first
#=> #<Asset id: 1, title: "An Asset">
#featured.current_post_asset #=> #<PostAsset id: 1, context: "featured">
How would that work? I've been banging my head over it all day :).
What currently happens is when I do this:
#post.featured_images << Asset.create!(:title => "An Asset")
Then the join model PostAsset that gets created never gets a chance to set context. How do I set that context property? It looks like this:
PostAsset.first #=> #<PostAsset id: 1, context: nil>
Update:
I have created a test gem to try to isolate the problem. Is there an easier way to do this?!
This ActsAsJoinable::Core class makes it so you can have many to many relationships with a context between them in the join model. And it adds helper methods. The basic tests show basically what I'm trying to do. Any better ideas on how to do this properly?
Look at the has_many options in the ActiveRecord::Associations::ClassMethods API located here: http://rails.rubyonrails.org/classes/ActiveRecord/Associations/ClassMethods.html#M001316
This is the most interesting quote:
:conditions
Specify the conditions that the associated object must meet in order to be included as a WHERE SQL fragment, such as authorized = 1. Record creations from the association are scoped if a hash is used. has_many :posts, :conditions => {:published => true} will create published posts with #blog.posts.create or #blog.posts.build.
So I believe your conditions must be specified as a hash, like so:
class Post < ActiveRecord::Base
has_many :post_assets
has_many :featured_post_assets, :conditions => { :context => 'featured' }
has_many :assets, :through => :post_assets
has_many :featured_images, :through => :featured_post_assets,
:class_name => "Asset", :source => :asset,
end
And you should also do the following:
#post.featured_images.build(:title => "An asset")
instead of:
#post.featured_images << Asset.create!(:title => "An Asset")
This should call the scoped asset build, as suggested in the quote above to add the context field to asset. It will also save both the join model object (post_asset) and the asset object to the database at the same time in one atomic transaction.
Suppose we have a photography site. Any author can subscribe to receive updates from any other author. Obviously if author A is subscribed to author B that doesn't mean that B is subscribed to A. So we build models
class Author < ActiveRecord::Base
has_many :subscriptions
has_many :subscribed_by_author, :through => :subscriptions, :source => :subscribed_to
end
class Subscription < ActiveRecord::Base
belongs_to :author
belongs_to :subscribed_to, :class_name => "Author", :foreign_key => "subscribed_to"
end
This way we can use
some_author.subscribed_by_author -- the list of the authors to whom some_author is subscribed.
For any subscription we can know both ends (who is subscribed to whom)
But the question is how to get the list of people subscribed to some author using only rails (not using plain SQL) i.e get the answer to :"Who is subscribed to some_author?"
Question: is there any ability in Rails to get the relationship working both sides i.e. not only writing some_author.subscribed_BY_author but having some_author_subscribed_TO_author? If there is one, then what is it?
P.S. Obvious solution is to
Change the database design, adding a column named "direction"
Create 2 records each time a subscription is created
Add to the author model
has_many :subscribed_BY_author, :through => :subscriptions, :source => :subscribed_to, :conditions => "direction = 'by'"
has_many :subscribed_TO_author, :through => :subscriptions, :source => :subscribed_to, :conditions => "direction = 'to'"
But i wonder if there is a solution without changing the database design.
I'd use plain HABTM for something simple like this, but you're going to need a join table no matter what.
create_table :subscriptions do |t|
t.column :author_id, :integer
t.column :subscriber_id, :integer
end
Point Author to it:
class Author < ActiveRecord::Base
has_and_belongs_to_many :subscribers
:class_name => "Author",
:join_table => "subscriptions",
:association_foreign_key => "subscriber_id"
def subscriptions # "subscribers" is already included above
self.subscribers.find(:all, :subscriber_id=>author.id) # hopefully not too
end # much SQL
end
If you're really committed to your method names:
def subscribed_to_author
subscribers
end
def subscribed_by_author(author)
self.subscribers.find(:all, :subscriber_id=>author.id)
end
Create some connections (I'd make SubscriptionsController to be RESTy)
SubscriptionsController < ApplicationController
def create
#author = Author.find(params[:author_id] # author to be subscribed to
#user = current_user # user clicking the "subscribe" button
#author.subscribers << #user # assuming authors should only
#author.save # be able to subscribe themselves
end
end
Display names, or whatever
#author.subscribers.each do |s|
s.name
end
# ...or...and...also...
<%= render :partial => #author.subscribers -%>
<%= render :partial => #author.subscriptions -%>
# Author model
has_many :subscriptions_to, :class_name => "Subscription", :foreign_key => "subscribed_to"
has_many :subscribed_to_author, :through => :subscriptions_to, :source => :author
As far as I know - it works! :)
I have a data model something like this:
# columns include collection_item_id, collection_id, item_id, position, etc
class CollectionItem < ActiveRecord::Base
self.primary_key = 'collection_item_id'
belongs_to :collection
belongs_to :item
end
class Item < ActiveRecord::Base
has_many :collection_items
has_many :collections, :through => :collection_items, :source => :collection
end
class Collection < ActiveRecord::Base
has_many :collection_items, :order => :position
has_many :items, :through => :collection_items, :source => :item, :order => :position
end
An Item can appear in multiple collections and also more than once in the same collection at different positions.
I'm trying to create a helper method that creates a menu containing every item in every collection. I want to use the collection_item_id to keep track of the currently selected item between requests, but I can't access any attributes of the join model via the Item class.
def helper_method( collection_id )
colls = Collection.find :all
colls.each do |coll|
coll.items.each do |item|
# !!! FAILS HERE ( undefined method `collection_item_id' )
do_something_with( item.collection_item_id )
end
end
end
I tried this as well but it also fails with ( undefined method `collection_item' )
do_something_with( item.collection_item.collection_item_id )
Edit: thanks to serioys sam for pointing out that the above is obviously wrong
I have also tried to access other attributes in the join model, like this:
do_something_with( item.position )
and:
do_something_with( item.collection_item.position )
Edit: thanks to serioys sam for pointing out that the above is obviously wrong
but they also fail.
Can anyone advise me how to proceed with this?
Edit: -------------------->
I found from online documentation that using has_and_belongs_to_many will attach the join table attributes to the retreived items, but apparently it is deprecated. I haven't tried it yet.
Currently I am working on amending my Collection model like this:
class Collection < ActiveRecord::Base
has_many :collection_items, :order => :position, :include => :item
...
end
and changing the helper to use coll.collection_items instead of coll.items
Edit: -------------------->
I've changed my helper to work as above and it works fine - (thankyou sam)
It's made a mess of my code - because of other factors not detailed here - but nothing that an hour or two of re-factoring wont sort out.
In your example you have defined in Item model relationship as has_many for collection_items and collections the generated association method is collection_items and collections respectively both of them returns an array so the way you are trying to access here is wrong. this is primarily case of mant to many relationship. just check this Asscociation Documentation for further reference.
do_something_with( item.collection_item_id )
This fails because item does not have a collection_item_id member.
do_something_with( item.collection_item.collection_item_id )
This fails because item does not have a collection_item member.
Remember that the relation between item and collection_items is a has_many. So item has collection_items, not just a single item. Also, each collection has a list of collection items. What you want to do is probably this:
colls = Collection.find :all
colls.each do |coll|
coll.collection_items.each do |collection_item|
do_something_with( collection_item.id )
end
end
A couple of other pieces of advice:
Have you read the documentation for has_many :through in the Rails Guides? It is pretty good.
You shouldn't need the :source parameters in the has_many declarations, since you have named your models and associations in a sensible way.
I found from online documentation that using has_and_belongs_to_many will attach the join table attributes to the retreived items, but apparently it is deprecated. I haven't tried it yet.
I recommend you stick with has_many :through, because has_and_belongs_to_many is more confusing and doesn't offer any real benefits.
I was able to get this working for one of my models:
class Group < ActiveRecord::Base
has_many :users, :through => :memberships, :source => :user do
def with_join
proxy_target.map do |user|
proxy_owner = proxy_owner()
user.metaclass.send(:define_method, :membership) do
memberships.detect {|_| _.group == proxy_owner}
end
user
end
end
end
end
In your case, something like this should work (haven't tested):
class Collection < ActiveRecord::Base
has_many :collection_items, :order => :position
has_many :items, :through => :collection_items, :source => :item, :order => :position do
def with_join
proxy_target.map do |items|
proxy_owner = proxy_owner()
item.metaclass.send(:define_method, :join) do
collection_items.detect {|_| _.collection == proxy_owner}
end
item
end
end
end
end
Now you should be able to access the CollectionItem from an Item as long as you access your items like this (items.with_join):
def helper_method( collection_id )
colls = Collection.find :all
colls.each do |coll|
coll.items.with_join.each do |item|
do_something_with( item.join.collection_item_id )
end
end
end
Here is a more general solution that you can use to add this behavior to any has_many :through association:
http://github.com/TylerRick/has_many_through_with_join_model
class Collection < ActiveRecord::Base
has_many :collection_items, :order => :position
has_many :items, :through => :collection_items, :source => :item, :order => :position, :extend => WithJoinModel
end