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

问题描述

我需要获取模型属性的列表，这些属性实际上是关系(也就是说，它们是由 relationship() 创建的).

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

假设我在 models 中有一个模型 Foo:

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')

稍后，我想使用 models.Thing 并获得一个关系属性列表，即 ['foo', 'bar'].

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

目前我正在检查 dir(models.Thing) 指示的每个属性，这些属性恰好是 sqlalchemy.orm.attributes.InstrumentedAttribute 类型的property 属性 — 可以是 ColumnProperty 或 RelationshipProperty.这样做可以，但我想知道是否还有其他方法.

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.

我可能只需找到以 _id 结尾的所有属性并导出关系名称，但在某些情况下这可能会中断.

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

如何设置 __relationships__ = ['foo', 'bar']?

或者 SQLAlchemy 中是否有内置的东西来帮助我?

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

推荐答案

确实有 - 看看 sqlalchemy.inspection.inspect.在映射类(例如，您的 Thing 类)上调用 inspect 将返回 Mapper，它有一个 relationships 属性，即 dict喜欢:

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 that is dict like:

from sqlalchemy.inspection import inspect

thing_relations = inspect(Thing).relationships.items()

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