我正在阅读教程并收到此错误：
.../sample_app/app/controllers/application_controller.rb
`<class:ApplicationController>': uninitialized constant SessionsHelper (NameError)
我尝试再次输入代码但无济于事，我猜我可能在某个地方打错了字。我研究了类似的问题，但它们要么太不同，要么我不理解给出的解决方案。
这是相关代码：
应用控制器
class ApplicationController < ActionController::Base
protect_from_forgery with: :exception
include ::SessionsHelper
end
session_controller
class SessionsController < ApplicationController
def new
end
def create
user = User.find_by_email(params[:session][:email].downcase)
if user && user.authenticate(params[:session][:password])
# Sign the user in and redirect to the user's show page.
sign_in user
redirect_to user
else
flash.now[:error] = 'Invalid email/password combination'
render 'new'
end
end
def destroy
end
end
用户页面规范
require 'spec_helper'
describe User do
before do
@user = User.new(name: "Example User", email: "user@example.com",
password: "foobar", password_confirmation: "foobar" )
end
subject { @user }
it { should respond_to(:name) }
it { should respond_to(:email) }
it { should respond_to(:password_digest) }
it { should respond_to(:password) }
it { should respond_to(:password_confirmation) }
it { should respond_to(:remember_token) }
it { should respond_to(:authenticate) }
...
任何帮助和解释什么是错误的以及如何解决它将不胜感激。