Tutorial :rails : what's wrong with this multiple join with conditions on the associations?



Question:

Here are my models:

class Deck < ActiveRecord::Base    belongs_to :game    has_many :deck_cards  end    class DeckCard < ActiveRecord::Base    belongs_to :card    belongs_to :deck  end    class Card < ActiveRecord::Base  end  

Here's my attempted find:

DeckCard.all :joins => [:card, :deck], :conditions => {{:decks => {:game_id => @game.id}}, {:cards => {:present => true}}}  

I keep getting the error : undefined method for all for #Class:0x4b2a98>. I'm assuming this is a misleading error from parsing my conditions. I'm following the guide for Active Record Query. I wasn't sure about whether to use the singular or plural form of the associations. Look like with a belongs_to, you're supposed to use singular form in the :joins hash, but I wasn't sure in the :conditions hash, so I tried both and neither worked.

In case it isn't clear, what I'm trying to do in SQL is:

SELECT * from DeckCards    INNER JOIN decks on decks.id = deck_cards.deck_id    INNER JOIN cards on card.id = deck_cards.card_id    WHERE decks.game_id = 4    AND cards.present = true  

I'm able to get around it for now by using DeckCard.find_by_sql, but it would be nice to figure out why the joins and conditions on associations isn't working.

I'm using InstantRails-2.0 on windows, which is using Rails 2.0.2

Edited : some progress using DeckCard.find(:all ...) instead. I also edited the brackets based on another answer. My latest code is

DeckCard.find :all, :joins => [:card, :deck], :conditions => {:deck => {:game_id => @game.id}, :cards => {:present => true}}    

which is producing the following error:

Unknown column 'deck_cards.decks' in 'where clause': SELECT `deck_cards`.* FROM `deck_cards`   INNER JOIN `cards` ON `cards`.id = `deck_cards`.card_id  INNER JOIN `decks` ON `decks`.id = `deck_cards`.deck_id  WHERE (`deck_cards`.`decks` = '--- \n- :game_id\n- 5\n' AND `deck_cards`.`cards` = '--- \n- :present\n- true\n')    

The joins appear correct but not the WHERE conditions. I've tried a few different things like :deck or :decks in the conditions clause but no luck. Could this be another difference between the current ActiveRecord Query Interface docs and how conditions are done in 2.0.2?

Thanks!


Solution:1

You need to complete your association with the Card model:

class Card < ActiveRecord::Base    has_many :deck_cards  end  

EDIT 2: Try this:

 DeckCard.find :all, :joins => [:card, :deck], :conditions => ["decks.game_id = ? and cards.present = ?", @game.id, true]  


Solution:2

Your :conditions contains 2 hashes. This is incorrect. You should have two keys (:decks and :cards) which should each have a hash as a value. Correct yours to look like this:

:conditions => {:decks => {:game_id => @game.id}, :cards => {:present => true}}  


Solution:3

I didn't test this, but what happens if you use...

DeckCard.find(:all, :include => [:cards, :deck], :conditions => {:deck => {:game_id => @game.id}, :cards => {:present => true}})  


Solution:4

What version of rails? ActiveRecord#all was added sometime after 2.0.2.

What does a puts DeckCard.respond_to?(:all) result in?


Solution:5

Your syntax is also backwards. I believe the join (and join table) needs to be arranged alphabetically. Hence card_decks. I believe this is the default configuration of rails. I had a problem similar to this once before I started using has_many => :through


Solution:6

@game.deck.deckcards.joins(:cards).where('cards.present' => true)

rails 4 syntax is much better


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