Question

My Model:

class Student < ActiveRecord::Base
has_many :lack_knowledge_points, :through => :knowledge_point_infos,
:conditions => ['knowledge_point_infos.level <= ?',10],:source => :knowledge_point

I want that 10 be dynamic

What is my best practice?

Define a method and find_by_sql? Or can Rails do something else for me?

Answer 1

I am not clear how you want ‘level’ to be dynamic. Anyway, you could use scope with lambda or define a method in the model.

#If you want it to return an array
def lack_knowledge_points(threshold)
  knowledge_point_infos.where('level <= ?', threshold).map{|info|info.knowledge_point}
end