ruby-on-rails – 在轨道上的ruby中未定义的方法’authenticate

这是我的Sessions_controller：

def new
end

def create
  user = User.find_by(email: params[:session][:email].downcase)
  if user && user.authenticate(params[:session][:passkey])
    # Log the user in and redirect to the user's show page.
  else
    # Create an error message.
  flash[:danger] = 'Invalid email/password combination' # Not quite right!
    render 'new'
  end
end

def destroy
end

这是我的观点：new.html.erb

<%= form_for(:session,url: login_path) do |f| %>

    <%= f.label :email %>
    <%= f.email_field :email,class: 'form-control' %>

    <%= f.label :passkey%>
    <%= f.password_field :passkey,class: 'form-control' %>

    <%= f.submit "Log in",class: "btn btn-primary" %>
<% end %>

这是我的模特：

class User< ActiveRecord::Base
  validates :first_name,:presence => true,:length => { :in => 3..20 }
  validates :last_name,:length => { :in => 3..20 }
  validates :email,:uniqueness => true,format: { with: /A[^@s]+@([^@.s]+.)+[^@.s]+z/ }
  validates :passkey,:confirmation => true,:length => {:in => 6..20}
end

当我单击“登录”按钮,然后显示此错误：

NoMethodError in SessionsController#create
undefined method `authenticate’ for #User:0x0000000d5c65e0>

我该如何解决这个错误？

我正在使用ruby 1.9.7 Rails 4.2.5& mysql2

那对我很有帮助,拜托.