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问题描述

我正在尝试两个新的东西,所以在简化和澄清的帮助是赞赏。

 从sqlalchemy.ext .declarative import声明
从sqlalchemy导入列,浮点,事件

类TimeStampMixin(对象):

@declared_attr
def __tablename __(cls):
return cls .__ name __。lower()

created =列(Float)
modified =列(Float)
def __init __(self,created = None,
modified = None)
self.created = created
self.modified = modified

def create_time(mapper,connection,target):
target。 create = time()

#def modified_time(mapper,connection,target):
#target.modified = time()

event.listen(TimeStampMixin, 'before_insert',create_time)
#event.listen(TimeStampMixin,'before_update',modified_time)

所以我想创建一个mixin我可以在任何类中申请:

  class MyClass(TimeStampMixin,Base):
等,etc,etc

此类继承了在创建时创建时间戳的功能,并在更新时创建/修改时间戳。 >

导入我收到此错误:

  raise exc.UnmappedClassError(class_) 
sqlalchemy.orm.exc.UnmappedClassError:类'db.database.TimeStampMixin'未映射

aaaand在这一点上我被困了。

解决方案

这是我在 before_insert 事件:将 classmethod 添加到您注册当前类和句柄的 TimeStampMixin 设置创建时间。



例如

  class TimeStampMixin(object) 

#其他类方法

@staticmethod
def create_time(mapper,connection,targe t):
target.created = time()

@classmethod
def register(cls):
sqlalchemy.event.listen(cls,'before_insert' cls.create_time)

这样,你可以:


  1. 轻松扩展和更改您收听的内容以及您注册的内容。

  2. 覆盖某些类的create_time方法

  3. 明确说明哪些方法需要设置时间戳。

您可以简单地使用它:

  class MyMappedClass(TimeStampMixin,Base):
pass

MyMappedClass.register()

简单,很清楚,没有魔法,但仍然像你想要的封装。


I am attempting 2 new things at once, so assistance in both simplifying and clarifying is appreciated.

from sqlalchemy.ext.declarative import declared_attr
from sqlalchemy import Column, Float, event

class TimeStampMixin(object):

    @declared_attr
    def __tablename__(cls):
        return cls.__name__.lower()

    created = Column(Float)
    modified = Column(Float)
    def __init__(self, created = None,
                       modified = None):
        self.created = created
        self.modified = modified

def create_time(mapper, connection, target):
    target.created = time()

#def modified_time(mapper, connection, target):
#    target.modified = time()

event.listen(TimeStampMixin, 'before_insert', create_time)
#event.listen(TimeStampMixin, 'before_update', modified_time)

So I want to create a mixin I can apply in any class:

class MyClass(TimeStampMixin, Base):
    etc, etc, etc

This class inherits functionality that creates a timestamp on creation and creates/modifies a timestamp on update.

on import I get this error:

raise exc.UnmappedClassError(class_)
sqlalchemy.orm.exc.UnmappedClassError: Class 'db.database.TimeStampMixin' is not mapped

aaaand I'm stumped at this point.

解决方案

Here's what I'd do to listen on before_insert events: add a classmethod to your TimeStampMixin that registers the current class and handles setting creation time.

E.g.

class TimeStampMixin(object):

    # other class methods

    @staticmethod
    def create_time(mapper, connection, target):
        target.created = time()

    @classmethod
    def register(cls):
        sqlalchemy.event.listen(cls, 'before_insert', cls.create_time)

That way, you can:

  1. Easily extend and change what you listen for and what you register.
  2. Override the create_time method for certain classes
  3. Be explicit about which methods need to have their timestamps set.

You can use it simply:

class MyMappedClass(TimeStampMixin, Base):
    pass

MyMappedClass.register()

Simple, very clear, no magic, but still encapsulates like you want.

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08-23 13:49