I have a table with entries, and each entries can have different account-types. I'm trying to define and return the account based on the value of cindof
Each account type has one table, account_site and account_page. So a regular belongs_to won't do.
So is there any way to return something like:
belongs_to :account, :class_name => "AccountSite", :foreign_key => "account_id" if cindof = 1
belongs_to :account, :class_name => "AccountPage", :foreign_key => "account_id" if cindof = 2
Have tried to do that in a method allso, but no luck. Really want to have just one accountand not different belongs_to names.
Anyone that can figure out what I want? Hard to explain in English.
Terw
You should be able to do what you want with a polymorphic association. This won't switch on cindof by default, but that may not be a problem.
class ObjectWithAccount < ActiveRecord::Base
belongs_to :account, :polymorphic => true
end
class AccountSite < ActiveRecord::Base
has_many :objects_with_accounts,
:as => :account,
:class_name => 'ObjectWithAccount'
end
class AccountPage < ActiveRecord::Base
has_many :objects_with_accounts,
:as => :account,
:class_name => 'ObjectWithAccount'
end
You will need both an account_id column and a account_type column. The type of the account object is then stored in the extra type column.
This will let you do:
obj.account = AccountPage.new
or
obj.account = AccountSite.new
I would look into Single Table Inheritance. Not 100% sure, but I think it would solve your problem http://code.alexreisner.com/articles/single-table-inheritance-in-rails.html
If that isn't good, this isn't too hard to implement yourself.
def account
case self.cindof
when 1 then AccountSite.find self.account_id
when 2 then AccountPage.find self.account_id
end
end
Related
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.
my problem is following. How can I joins belongs_to association from polymorphic model
There is situation
opinion.rb
class Opinion < ActiveRecord::Base
belongs_to :opinionable, :polymorphic => true
belongs_to :category
end
answer.rb
class Answer < ActiveRecord::Base
has_many :opinions, :as => :opinionable
end
How can i do following
Opinion.joins(:opinionabe).all
it will throw
ArgumentError: You can't create a polymorphic belongs_to join without specifying the polymorphic class!
How can i specific which class i want to join?
Second question. How to preload it?
Opinion.preload(:opinionable).all
works fine. It will do query for each class in belongs_to.
But. if i want to do something like
Opinion.preload(:opinionable => :answer_form).all
there is problem because one model has this association and second hasn't. So it will throw exception.
So how i can do something like
Opinion.preload(:answer => :answer_form, :another_belongs_to_model).all
?
Thanks, David!
Actually if you just do
belongs_to :opinionable_answer, :foreign_key => :opinionable_id, :class_name => "Answer", conditions: { opinions: { opinionable_type: "Answer"}}
then you can do
Opinion.joins(:opinionable_answer).where(answers: { awesome: true})
It looks like you have not specified opinionable_type:string column for your Opinion model.
Try to update your migration in this manner:
class CreateOpinions < ActiveRecord::Migration
def self.up
create_table :opinions do |t|
t.integer :opinionable_id
t.string :opinionable_type
# ... other fields
t.timestamps
end
end
def self.down
drop_table :opinions
end
end
This will solve your second question and Opinion.preload(:opinionable).all should work well.
You cann't do joins on polymorphic association because they can be located in different tables, which are detected after Opinion model is loaded. That why model needs column opinionable_type.
If you try to do this you'll get next exception
ActiveRecord::EagerLoadPolymorphicError: Can not eagerly load the polymorphic association :opinionable
UPD: Added magic join ^_^
class Opinion < ActiveRecord::Base
belongs_to :opinionable, :polymorphic => true
belongs_to :opinionable_answer, :foreign_key => :opinionable_id, :class_name => "Answer"
scope :by_type, lambda { |type| joins("JOIN #{type.table_name} ON #{type.table_name}.id = #{Opinion.table_name}.opinionable_id AND #{Opinion.table_name}.opinionable_type = '#{type.to_s}'") }
end
Example:
Opinion.by_type(Answer).to_sql
=> "SELECT \"opinions\".* FROM \"opinions\" JOIN answers ON answers.id = opinions.opinionable_id AND opinions.opinionable_type = 'Answer'"
I know this question is old but I just spent an hour looking for the solution to a similar problem (Rails 3) and the only way I got it to work was the solution stated here: https://stackoverflow.com/a/25966630/6878997
Which, in your case would be:
class Opinion < ActiveRecord::Base
# The true polymorphic association
belongs_to :opinionable, polymorphic: true
# The trick to solve this problem
has_one :self_ref, :class_name => self, :foreign_key => :id
has_one :answer, :through => :self_ref, :source => :opinionable, :source_type => Answer
end
Seems tricky but this way you will be able to do multiple chained joins such as:
joins(answer: :other_model).
And whenever opinion.opinionable is not an Answer, opinion.answer will return nil.
Hope it helps somebody!
I've been using the association_collection method "other_ids" throughout my Rails app with no issues. However whenever I try to access it from within the model defining the association, Rails has no idea what I'm taking about. For example:
class Membership < ActiveRecord::Base
belongs_to :course, :touch => true
belongs_to :person, :touch => true
end
class Day < ActiveRecord::Base
belongs_to :course, :touch => true, :counter_cache => true
has_many :presents, :dependent => :delete_all
has_many :people, :through => :presents
before_destroy :clear_attendance
def clear_attendance
mems = Membership.where(:course_id => course.id, :person_id => person_ids)
mems.update_all(["attendance = attendance - ?", (1 / course.days.size.to_f)])
end
end
In this case, person_ids is always null. I've tried self.person_ids, people.ids, etc. All nothing. I have used day.person_ids elsewhere with no issues, so why can't I use it here?
I am using Ruby 1.9.1 and Rails 3.0.3. Here is the SQL call from my log:
[1m[36mAREL (0.0ms)[0m [1mUPDATE "memberships" SET attendance = attendance - 0.3333333333333333 WHERE ("memberships"."course_id" = 4) AND ("memberships"."person_id" IN (NULL))[0m
edit: added more code to clarify question
What you really want there is:
def a_method
self.people.all
end
But to answer your question, person_ids is the correct method, and it should return an empty array, not nil. I just tried an association like that out in 2.3.10. Maybe you can post some more of your code, rails version, etc.
Thanks for your help - I figured it out myself. The problem was the order of my callbacks. I was trying to call person_ids after the association had been deleted. Changing the order to this solved my issues.
class Day < ActiveRecord::Base
before_destroy :clear_attendance
belongs_to :course, :touch => true, :counter_cache => true
has_many :presents, :dependent => :delete_all
has_many :people, :through => :presents
I have these models simplified:
class Game::Champ < ActiveRecord::Base
has_one :contract, :class_name => "Game::ChampTeamContract", :dependent => :destroy
has_one :team, :through => :contract
# Attributes: :avg => integer
end
#
class Game::Team < ActiveRecord::Base
has_many :contracts, :class_name => "Game::ChampTeamContract", :dependent => :destroy
has_many :champs, :through => :contracts
end
#
class Game::ChampTeamContract < ActiveRecord::Base
belongs_to :champ
belongs_to :team
# Attributes: :expired => bool, :under_negotiation => bool
end
#
So what I want to do here is to find all Game::Champs that have no Game::ChampTeamContract whatsoever OR has, but (is not :under_negociation OR is :expired ), sorted by Champ.avg ASC
I am kinda stuck at using two queries, concating the result and sorting it. I wish there were a better way to to it more "Railish"
UPDATE: Just added a constraint about :expired
Try something like:
Game::Champs.
joins("left outer join game_champ_team_contracts on game_champ_team_contracts.champ_id = game_champs.id").
where("game_champ_team_contracts.id is null or (game_champ_team_contracts.state != ? or game_champ_team_contracts.state = ?)", :under_negotiation, :expired).
order("game_champs.avg ASC")
This is a fairly nasty line if left as-is, so if you use this, it needs tidying up. Use scopes or methods to split it up as much as possible!
I just tested with a super simple query:
#bars1 = Bar.where(:something => 1)
#bars2 = Bar.where(:something => 2)
#bars = #bars1 + #bars2
Not sure if it's right, but it works...
Hi i have these classes:
class Core < ActiveRecord::Base
belongs_to :resource, :polymorphic => true
belongs_to :image, :class_name => 'Multimedia', :foreign_key => 'image_id'
end
class Place < ActiveRecord::Base
has_one :core, :as => :resource
end
If i try do launch this:
a = Place.find(5)
a.name ="a"
a.core.image_id = 24
a.save
name is saved. image_id no
i want save automatically all changes in records in relationship with place class at a.save command. is possible?
thanks
Use :autosave => true
See section titled One-to-many Example for ActiveRecord::AutosaveAssociation.
You'll want something like:
class Place
has_one :core, :as => :resource, :autosave => true
end
Disclaimer:
The :autosave => true should be used on the "parent" Object. It works great with has_one and has_many, but I've run into great difficulty attempting to use it on a belongs_to. relationship.
I think that you can use the build_association method to do that. For example,
a = Place.find(5)
a.name = "a"
a.build_core(:image_id => 24)
a.save
But it might only work if the place object was created before hand.