ruby on rails - undefined local variable or method `signin' for #<Class:0x31fa7f0> -

i have following error in model class. how approach such errors.

class user < activerecord::base   # include default devise modules. others available are:   # :confirmable, :lockable, :timeoutable , :omniauthable   devise :database_authenticatable, :registerable,          :recoverable, :rememberable, :trackable, :validatable    attr_accessor :signin   validates :username, :uniqueness => {:case_sensitive => false}    def self.find_first_by_auth_conditions(warden_conditions)     puts warden_conditions     conditions = warden_conditions.dup     where(conditions).where(["lower(username) = :value or              lower(email)= :value", { :value => signin.downcase }]).first   end  end   

i new rails , learning things doing. how debug such issues. if such error in model, should first look.

this method devise, auth pair username , email or else. problem in signin variable use login instead code:

def self.find_first_by_auth_conditions(warden_conditions)     conditions = warden_conditions.dup     if login = conditions.delete(:login)       if login.start_with?('+')         where(["phone = :value , phone_confirm = :phone_confirm", { value: login.downcase, phone_confirm: true }]).first       else         where(["lower(email) = :value", { value: login.downcase }]).first       end     else       where(conditions).first     end   end