python - SQLAlchemy 等效于 ActiveRecord 中的命名范围

Question

是否有相当于 AR 的命名范围？命名范围基本上是过滤器，可以包装在方法中，然后链接。

这是来自http://archives.ryandaigle.com/articles/2008/8/20/named-scope-it-s-not-just-for-conditions-ya-know的示例：

class Article < ActiveRecord::Base

  # Get all articles that have been published
  named_scope :published, :conditions => ['published = ?', true]

  # Get all articles that were created recently
  named_scope :recent, lambda { { :conditions => ['created_at >= ?', 1.week.ago] } }

end

# Get all recently created articles that have been published
Article.published.recent

这是一个使用 Django ORM 的示例：http: //furrybrains.com/2009/06/22/named-scopes-for-django/

Answer 1

SQLAlchemy 具有混合属性，您可以使用它来构建任何类型的系统：

from sqlalchemy.ext.hybrid import hybrid_property


class Article(Base):
    @hybrid_property
    def published(self):
        return self.is_published == True

    @hybrid_property
    def recent(self):
        # this relies on the date arithmetic of the target backend
        return datetime.now() - self.created_at >= datetime.timedelta(days=7)


articles = query(Article).filter(Article.published, Article.recent).all()