Hacking ActiveRecord：添加全局命名范围

Question

我正在尝试为像这样的 ActiveRecord 模型提供一组非常通用的命名范围：

module Scopes
  def self.included(base)
    base.class_eval do
      named_scope :not_older_than, lambda {|interval|
        {:conditions => ["#{table_name}.created_at >= ?", interval.ago]
      }
    end
  end
end
ActiveRecord::Base.send(:include, Scopes)

class User < ActiveRecord::Base
end

如果命名范围应该是通用的，我们需要指定 *table_name* 以防止它们是来自其他链式命名范围的连接时出现命名问题。

问题是我们无法获取 table_name，因为它是在 ActiveRecord::Base 而不是 User 上调用的。

User.not_older_than(1.week)

NoMethodError: undefined method `abstract_class?' for Object:Class
from /var/lib/gems/1.8/gems/activerecord-2.3.5/lib/active_record/base.rb:2207:in `class_of_active_record_descendant'
from /var/lib/gems/1.8/gems/activerecord-2.3.5/lib/active_record/base.rb:1462:in `base_class'
from /var/lib/gems/1.8/gems/activerecord-2.3.5/lib/active_record/base.rb:1138:in `reset_table_name'
from /var/lib/gems/1.8/gems/activerecord-2.3.5/lib/active_record/base.rb:1134:in `table_name'
from /home/bogdan/makabu/railsware/startwire/repository/lib/core_ext/active_record/base.rb:15:in `included'
from /var/lib/gems/1.8/gems/activerecord-2.3.5/lib/active_record/named_scope.rb:92:in `call'
from /var/lib/gems/1.8/gems/activerecord-2.3.5/lib/active_record/named_scope.rb:92:in `named_scope'
from /var/lib/gems/1.8/gems/activerecord-2.3.5/lib/active_record/named_scope.rb:97:in `call'
from /var/lib/gems/1.8/gems/activerecord-2.3.5/lib/active_record/named_scope.rb:97:in `not_older_than'

如何在 Scopes 模块中获取实际的 table_name？

Answer 1

尝试在 ActiveRecord::Base 的类方法中使用#scoped 方法。这应该有效：

module Scopes
  def self.included(base)
    base.class_eval do
      def self.not_older_than(interval)
        scoped(:conditions => ["#{table_name}.created_at > ?", interval.ago])
      end
    end
  end
end

ActiveRecord::Base.send(:include, Scopes)

Answer 2

Rails 5，ApplicationRecord（希望对其他人有所帮助）

# app/models/concerns/not_older_than.rb

module NotOlderThan
  extend ActiveSupport::Concern

  included do
    scope :not_older_than, -> (time, table = self.table_name){ 
      where("#{table}.created_at >= ?", time.ago)
    }
  end
end

# app/models/application_record.rb

class ApplicationRecord < ActiveRecord::Base
  self.abstract_class = true
  include NotOlderThan
end

# app/models/user.rb
class User < ApplicationRecord
  # Code
end

# Usage
User.not_older_than(1.week)

在 Rails 5 中，所有模型默认继承自 ApplicationRecord。如果您想将此范围仅应用于特定的模型集，请仅将包含语句添加到这些模型类。这也适用于连接查询和链式作用域。

Answer 3

以下其他有用的范围：

module Scopes
  def self.included(base)
    base.class_eval do
      def self.created(date_start, date_end = nil)
          if date_start && date_end
            scoped(:conditions => ["#{table_name}.created_at >= ? AND #{table_name}.created_at <= ?", date_start, date_end])
          elsif date_start
            scoped(:conditions => ["#{table_name}.created_at >= ?", date_start])
          end
      end
      def self.updated(date_start, date_end = nil)
          if date_start && date_end
            scoped(:conditions => ["#{table_name}.updated_at >= ? AND #{table_name}.updated_at <= ?", date_start, date_end])
          elsif date_start
            scoped(:conditions => ["#{table_name}.updated_at >= ?", date_start])
          end
      end
    end
  end
end

ActiveRecord::Base.send(:include, Scopes)

Answer 4

这是一个更新的、兼容 Rails4 的解决方案。
有人告诉我，像这样定义全局范围可能会导致冲突，caveat emptor 等等，但有时您只需要在所有模型上设置一个简单的范围，对吧？

定义一个模块。

# in /app/models/concerns/global_scopes.rb
module GlobalScopes
  def self.included(base)
    base.class_eval do
      def self.in_daterange(start_date, end_date)
        all.where(created_at: start_date.to_date.beginning_of_day..end_date.to_date.end_of_day)
      end
    end
  end
end

将模块包含在ActiveRecord::Base中。

# in /config/initializers/activerecord.rb
ActiveRecord::Base.send(:include, GlobalScopes)

就是这样！请注意，在 Rails4 中，您不必乱用 :scoped，而是使用 :all 并将查询链接到它。