(Crossposting note: Since I didn’t get any response here, I posted this
also on
ruby on rails - RubyOnRails: counting the result of a join - Stack Overflow)
I have in my model :dicts, :cards and :idioms. Each Dict has many Cards
and each Cards has many Idioms. Also, :idioms has an Integer column
:kind.
I would like to find out, whether a certain dict object has at least
one Card which has at least one Idiom where :kind has a certain value.
This is my (working) code:
def has_kind?(dict,kind)
Card. joins(:idioms). where(“dict_id=#{dict.id} and
cards.id=idioms.card_id and kind=#{kind}”). count > 0
end
This works, but can it be done better? I also tried to omit at least one
of the id comparision by doing something like:
dict.cards.where(“cards.id = …”).count > 0
but this doesn’t work (“count” is not applicable in this case).