target_model_class = Object.const_get(target) # target == 'business_areas' - passed as argument source_model_class = Object.const_get(source) # source == 'business_applications' - passed as argument
attributes = params[...] # values from a form in a view source_instance = source_model_class.find(...) # id from view target_instance = target_model_class.create! attributes source_instance.method(target) << target_instance unless source_instance.nil? source_instance.save
But gets the following error complaining << method does not exist:
undefined method `<<' for #<Method: BusinessApplication#business_areas>
You don't need to use #method method : you don't want to manipulate a Method object but you just want to send a message whose name is an association.
You should look at : source_instance.send(target)