Ruby on rails 语法错误意外的tANDOP on rails 3教程

我想我忽略了一些愚蠢的事情，但我遵循的是rails 3教程，如果用户对未发布的文章发表评论，我会添加错误……因此在rails控制台中，我尝试通过输入以下代码来创建对“未发布”文章（草稿）的评论

>> article = Article.draft.first
=> #<Article id: 7, title: "One-to-many associations",        ...> 
>> comment = article.comments.create :name => 'Dude', :email => 'dude@example.com', :body    => 'Great article!'

以下是我的文章模型：

class Article < ActiveRecord::Base
  attr_accessible :body, :published_at, :title

  validates :title, :presence => true
  validates :body, :presence => true

  belongs_to :user
  has_and_belongs_to_many :categories
  has_many :comments

  scope :published, where("articles.published_at IS NOT NULL")
  scope :draft, where("articles.published_at IS NULL")
  # recent post from < a month ago - see pg 103 of tutorial
  # scope :recent, lambda { published.where("articles.published_at > ?", 1.month.ago.to_date)}
  scope :where_title, lambda { |term| where("articles.title LIKE ?", "%#{term}%") }

  def long_title
    "#{title} - #{published_at}"
  end

  def published?
    published_at.present?
  end
end

类文章true
验证：body，：presence=>true
属于：用户
_和_是否属于多个类别
有很多评论
范围：已发布，其中（“articles.published_at不为空”）
范围：草稿，其中（“articles.published_at为空”）
#最近发表的文章<一个月前-参见教程第103页
#范围：最近，lambda{published.where（“articles.published_at>？”，1.month.ago.to_date）}
范围：where_title，lambda{term}where（“articles.title LIKE？”，“%{term}%”
def long_标题
“#{title}-#{published_at}”
结束
def发布了吗？
现在出版了吗？
结束
结束

请让我知道，如果我需要提供任何其他…我感谢任何和所有的帮助…非常感谢

更新：

在遵循iltempos提示之后…我现在得到以下验证错误

ArgumentError：您至少需要提供一个验证 来自/opt/local/lib/ruby/gems/1.8/gems/activemodel-3.2.3/lib/active\u model/validations/validates.rb:86:in

validates'
from/Users/bbarton250/Sites/rails_projects/theoldman/app/models/comment.rb:7
从/opt/local/lib/ruby/gems/1.8/gems/activesupport-3.2.3/lib/active\u support/dependencies.rb:469:in

load' 从/opt/local/lib/ruby/gems/1.8/gems/activesupport-3.2.3/lib/active\u support/dependencies.rb:469:in

load\u文件'
从/opt/local/lib/ruby/gems/1.8/gems/activesupport-3.2.3/lib/active\u support/dependencies.rb:639:in

new\u constants\u in' 来自/opt/local/lib/ruby/gems/1.8/gems/activesupport-3.2.3/lib/active\u support/dependencies.rb:468:in

load\u文件'
从/opt/local/lib/ruby/gems/1.8/gems/activesupport-3.2.3/lib/active\u support/dependencies.rb:353:in

require\u或\u load' 从/opt/local/lib/ruby/gems/1.8/gems/activesupport-3.2.3/lib/active\u support/dependencies.rb:502:in

load\u missing\u constant'
从/opt/local/lib/ruby/gems/1.8/gems/activesupport-3.2.3/lib/active\u-support/dependencies.rb:192:in

const\u-missing' 来自/opt/local/lib/ruby/gems/1.8/gems/activesupport-3.2.3/lib/active\u support/dependencies.rb:190:in

each'
从/opt/local/lib/ruby/gems/1.8/gems/activesupport-3.2.3/lib/active\u support/dependencies.rb:190:in

const\u missing' 从/opt/local/lib/ruby/gems/1.8/gems/activesupport-3.2.3/lib/active\u support/dependencies.rb:514:in

load\u missing\u constant'
从/opt/local/lib/ruby/gems/1.8/gems/activesupport-3.2.3/lib/active\u-support/dependencies.rb:192:in

const\u-missing' 来自/opt/local/lib/ruby/gems/1.8/gems/activesupport-3.2.3/lib/active\u support/dependencies.rb:190:in

each'
从/opt/local/lib/ruby/gems/1.8/gems/activesupport-3.2.3/lib/active\u support/dependencies.rb:190:in

const\u missing' 来自/opt/local/lib/ruby/gems/1.8/gems/activesupport-3.2.3/lib/active\u-support/endictor/methods.rb:218:in

constantize'
来自/opt/local/lib/ruby/gems/1.8/gems/activesupport-3.2.3/lib/active\u-support/endictor/methods.rb:217:in

each' 来自/opt/local/lib/ruby/gems/1.8/gems/activesupport-3.2.3/lib/active\u-support/endoctor/methods.rb:217:in

constantize'
从/opt/local/lib/ruby/gems/1.8/gems/activesupport-3.2.3/lib/active\u support/dependencies.rb:554:in

get' 来自/opt/local/lib/ruby/gems/1.8/gems/activesupport-3.2.3/lib/active\u support/dependencies.rb:588:in

constantize'
从/opt/local/lib/ruby/gems/1.8/gems/activerecord-3.2.3/lib/active\u record/heritation.rb:111:in

compute\u type' 来自/opt/local/lib/ruby/gems/1.8/gems/activerecord-3.2.3/lib/active\u record/heritation.rb:109:in

每个'
从/opt/local/lib/ruby/gems/1.8/gems/activerecord-3.2.3/lib/active\u record/heritation.rb:109:in

compute\u type' 从/opt/local/lib/ruby/gems/1.8/gems/activerecord-3.2.3/lib/active\u record/reflection.rb:172:in

send'
从/opt/local/lib/ruby/gems/1.8/gems/activerecord-3.2.3/lib/active\u record/reflection.rb:172:in

klass' 来自/opt/local/lib/ruby/gems/1.8/gems/activerecord-3.2.3/lib/active\u record/associations/collection\u association.rb:148:in

transaction'
从/opt/local/lib/ruby/gems/1.8/gems/activerecord-3.2.3/lib/active\u record/associations/collection\u association.rb:431:in

create\u record' 来自/opt/local/lib/ruby/gems/1.8/gems/activerecord-3.2.3/lib/active\u record/associations/collection\u association.rb:119:in

create'
从/opt/local/lib/ruby/gems/1.8/gems/activerecord-3.2.3/lib/active\u record/associations/collection\u proxy.rb:46:in

发送'

---

从/opt/local/lib/ruby/gems/1.8/gems/activerecord-3.2.3/lib/active\u record/associations/collection\u proxy.rb:46:in“create”

看起来有一个不应该出现的换行符：

  def article_should_be_published
    errors.add(:article_id, "is not published yet") if article && !article.published?
  end

---

谢谢iltempo…不过我现在得到了新的错误。我已经把它包括在上面了。关于这个“需要提供至少一个验证”错误有什么想法吗？不管怎样，我使用了“验证：”当我应该使用“验证：”…thx来获得帮助时

class Article < ActiveRecord::Base
  attr_accessible :body, :published_at, :title

  validates :title, :presence => true
  validates :body, :presence => true

  belongs_to :user
  has_and_belongs_to_many :categories
  has_many :comments

  scope :published, where("articles.published_at IS NOT NULL")
  scope :draft, where("articles.published_at IS NULL")
  # recent post from < a month ago - see pg 103 of tutorial
  # scope :recent, lambda { published.where("articles.published_at > ?", 1.month.ago.to_date)}
  scope :where_title, lambda { |term| where("articles.title LIKE ?", "%#{term}%") }

  def long_title
    "#{title} - #{published_at}"
  end

  def published?
    published_at.present?
  end
end

  def article_should_be_published
    errors.add(:article_id, "is not published yet") if article && !article.published?
  end