Interaction of model methods rails -

Interaction of model methods rails -

inside "course" model:

one method supposed select user_ids belong course

def participants course.joins(:click).pluck(:user_id) end

the other method supposed pick random user_id

def set_winner course.participants.sample end

however, next error:

undefined method `participants' #<class:0x007fc639811468>

if explain me, why doesn't work, i'd grateful.

your illustration doesn't work because define instance methods. , seek run them on class if class methods.to prepare write:

def self.participants course.joins(:click).pluck(:user_id) end def self.set_winner course.participants.sample end

or, improve

class course of study < activerecord::base scope :participants, -> { joins(:click).pluck(:user_id) } scope :set_winner, -> { participants.sample } end

ruby-on-rails ruby-on-rails-4 model