counting the result of a join

rubyonrails-talk
1

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).

2

The solution is found here:

Basically, I need to specify in my :dicts model, that there is an association to :cards

# in class Dict: has_many :idioms, through: :cards

After this, I can do:

idioms.where(kind: kind).exists?