Add element to rails has_many relation "dynamically"

Question

Having the following models:

class Card < ActiveRecord:Base
  # ...whatever
  belongs_to :model
end

class Model < ActiveRecord:Base
  # attribute: rank
  has_many  :cards
end

Considering the following code:

  mod = Model.new
  card = Card.first
  an_attribute = "rank"
  another_attribute = "cards"

  mod.send("#{an_attribute}=", 1) # this works fine, OK
  mod.cards << card      # this works fine as well, OK
  mod.send("#{another_attribute}<<", card) # this does not work, hence my question

The last line of code returns an error undefined method 'cards<<'

So my question is: how can I append the card element to mod.cards while accessing the cards has_many relation via a variable, i.e. by storing the name of the association in a variable ?

Answer 1

mod.send("#{another_attribute}").push(card)