I have the following models in which I join the Language and Products table via the Translation table using the Rails has_many :through paradigm:
class Language < ActiveRecord::Base
has_many :translations
has_many :products, :through => :translations
end
class Translation < ActiveRecord::Base
belongs_to :product
belongs_to :language
end
class Product < ActiveRecord::Basehas_many :translations
has_many :translations
has_many :languages, :through => :translations
end
I want to find the English Language Translation for a particular Product.
I can list the associated Languages and Translations:
prod开发者_如何学运维 = Product.find(4)
en = Language.find(:first, :conditions => { :lang_code => 'en' })
puts prod.translations
puts prod.languages
This prints:
#<Translation:0x11022a4>
#<Translation:0x1102114>
#<Language:0x602070>
#<Language:0x602020>
(There is an English and French translation for this product.)
How can I get the Translation for prod
corresponding to the en
Language?
If that doesn't make sense, here is the equivalent SQL:
SELECT t.* FROM products p, translations t, languages l WHERE l.id = t.language_id AND p.id = t.product_id AND l.lang_code = 'en';
You'd need something along this:
product = Product.find(4)
translation = product.translations.find(:first,:joins=>:languages, :conditions=>{:language=>{:lang_code=>'en'}})
The code will produce a join of Translations with Languages and filter accordingly your lang_code.
If the brackets confuse you a bit (I know sometimes they do) you could also do something like this:
translation = product.translations.find(:first,:joins=>:languages, :conditions=>["languages.lang_code like ?",'en'])
That last bit should produce the same SQL query, joining Translations with Language and then filtering by it's lang_code.
Yaraher's answer works, although I found a simpler way to accomplish the same thing:
t = Translation.find(:first,
:conditions => { :product_id => prod.id,
:language_id => lang.id })
精彩评论