黑客ActiveRecord：添加全局命名范围

Question

我试图为ActiveRecord模型提供一组非常通用的命名范围，如下所示：

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 *以防止命名问题（如果它们是来自其他链式命名范围的连接）。

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

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

Rails 5，ApplicationRecord（希望它能帮助别人）

# 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，默认情况下所有模型都从ApplicationRecord继承。如果您只想将此范围应用于特定模型集，请仅将include语句添加到这些模型类。这适用于连接查询和链接范围。

Answer 2

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

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 3

其他有用的范围如下：

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Rails4兼容解决方案。 我被告知定义这样的全球范围可能会导致冲突，警告和所有这些，但有时你只需要在所有模型上使用简单的范围，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)

而已！请注意，在Rails4中，您不必使用：scoped，而是使用：all并将查询链接到它。