SQLAlchemy，Flask：从db.Model获取关系 [英] SQLAlchemy, Flask: get relationships from a db.Model

问题描述

我需要得到一个模型属性的列表，这些属性实际上是关系的（也就是说，它们是由 relationship（））创建的。 b

假设我在模型中有一个模型 Foo ：

  class Thing（db.Model）：
 id = db.Column（...）
 bar_id = db.Column ...）
 foo_id = db.Column（...）
 foo = db.relationship（'Foo'）
 bar = db.relationship（'Bar'）
  

稍后，我想要 models.Thing 并获取关系属性列表，即 ['foo'，'bar'] 。



目前我正在检查由 dir（models.Thing） code> sqlalchemy.orm.attributes.InstrumentedAttribute 为它的属性的类属性 - 可以是 ColumnProperty 或 RelationshipProperty 。这样做的工作，但我想知道是否有另一种方式。

我可能只是找到所有以 _id 和派生关系名称，但这可能会打破一些情况下。



如何设置 __ relationships__ = ['foo'，'bar' ] ？

或者是在SQLAlchemy中内置了哪些东西来帮助我？

解决方案

确实有 - 请看 sqlalchemy.inspection.inspect 。在映射类（例如， Thing 类）上调用 inspect 将返回一个 Mapper ，它有一个< a href =http://docs.sqlalchemy.org/en/rel_0_9/orm/mapper_config.html#sqlalchemy.orm.mapper.Mapper.relationships> 关系 属性：

  from sqlalchemy.inspection import inspect 
 
 thing_relations = inspect（Thing）。关系
  

I need to get a list of a model's properties which are actually relationships (that is, they were created by relationship()).

Say I have a model Foo in a models:

class Thing(db.Model):
    id = db.Column(...)
    bar_id = db.Column(...)
    foo_id = db.Column(...)
    foo = db.relationship('Foo')
    bar = db.relationship('Bar')

Later on, I want to take models.Thing and get a list of relationship-properties, that is ['foo', 'bar'].

Currently I'm checking every attribute indicated by dir(models.Thing) that happens to be of type sqlalchemy.orm.attributes.InstrumentedAttribute for the class of its property attribute — which can be either a ColumnProperty or RelationshipProperty. This does the job but I was wondering if there's another way.

I could probably just find all attributes ending in _id and derive the relationship name, but this could break for some cases.

How about setting a __relationships__ = ['foo', 'bar']?

Or is there something built into SQLAlchemy to help me out?

解决方案

There is indeed - take a look at sqlalchemy.inspection.inspect. Calling inspect on a mapped class (for example, your Thing class) will return a Mapper, which has a relationships attribute:

from sqlalchemy.inspection import inspect

thing_relations = inspect(Thing).relationships

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