Finding activities Member's followers

gistfile1.rb

#"SELECT "activities".* FROM "activities" WHERE "activities"."member_id" IN (SELECT "members"."id" 
#FROM "members" 
#INNER JOIN "member_followers" ON "member_followers"."following_member_id" = "members"."id" 
#WHERE "member_followers"."follower_id" = 1491)"  

  def time_line
    members = Member.arel_table
    member_followers = MemberFollower.arel_table
    condition=(member_followers[:follower_id].eq(self.id))
    Activity.where(:member_id =>Member.select(members[:id]).joins(:member_followers).on(member_followers[:following_member_id].eq(members[:id])).where(condition))
  end