在使用 Flask、Graphene 时遇到了问题。考虑以下。
模型项目.model.site:
from project import db
from project.models import user
from datetime import datetime
class Site(db.Model):
__tablename__ = 'sites'
id = db.Column(db.Integer(), primary_key=True)
owner_id = db.Column(db.Integer, db.ForeignKey('users.id'))
name = db.Column(db.String(50))
desc = db.Column(db.Text())
location_lon = db.Column(db.String(50))
location_lat = db.Column(db.String(50))
creation_date = db.Column(db.DateTime(), default=datetime.utcnow())
users = db.relationship(
user,
backref=db.backref('users',
uselist=True,
cascade='delete,all'))
模型架构(project.schemas.site_schema)
from graphene_sqlalchemy import SQLAlchemyObjectType
from project.models import site as site_model
import graphene
class SiteAttributes:
owner_id = graphene.ID(description="Site owners user.id")
name = graphene.String(description="Site Name")
desc = graphene.String(description="Site description")
location_lon = graphene.String(description="Site Longitude")
location_lat = graphene.String(description="Site Latitude")
creation_date = graphene.DateTime(description="Site Creation Date")
class Site(SQLAlchemyObjectType, SiteAttributes):
"""Site node."""
class Meta:
model = site_model
interfaces = (graphene.relay.Node,)
最后是我计划公开 GraphQL api (project.schemas.schema)) 的主模式
from graphene_sqlalchemy import SQLAlchemyConnectionField
import graphene
from project.schemas import site_schema, trade_schema, user_schema
class Query(graphene.ObjectType):
"""Query objects for GraphQL API."""
node = graphene.relay.Node.Field()
user = graphene.relay.Node.Field(user_schema.User)
userList = SQLAlchemyConnectionField(user_schema.User)
site = graphene.relay.Node.Field(site_schema.Site)
siteList = SQLAlchemyConnectionField(site_schema.Site)
trade = graphene.relay.Node.Field(trade_schema.Trade)
tradeList = SQLAlchemyConnectionField(trade_schema.Trade)
schema = graphene.Schema(query=Query)
如果我在启动时加载模型,一切都很好。迁移发生,应用程序运行得很好。如果我通过架构加载模型,但应用程序会失败并显示以下消息:
AssertionError: You need to pass a valid SQLAlchemy Model in Site.Meta, received "<module 'project.models.site' from '/vagrant/src/project/models/site.py'>".
我用flask_sqlalchemy初始化了SQLAlchemy。这让我想知道创建的模型是否不被视为有效的 SQLAlchemy 模型?或者我在这里犯了一个我没有看到的基本错误。我假设是后者。
根据错误消息,似乎
project.models.site
(在第二个片段中使用 from project.models import site as site_model
导入)是一个 Python 模块,而不是 db.Model
或类似模块的子类。您是否想导入 Site
(大写)而不是 site
?
因此,将包修复到类中最终让我朝着正确的方向前进。事实证明,问题比这更深刻。实现这一点的唯一方法是阅读隐藏的异常。
首先,我确保加载的是实际模型而不是模块。非常感谢你@jwodder
最终这https://github.com/graphql-python/graphene-sqlalchemy/issues/121最终为我指明了正确的方向。通过检查实际的异常消息,我找到了解决方案
我发现这是由于graphene_sqlalchemy源代码中的这个断言造成的:(位于
graphene_sqlalchemy/types.py
)
assert is_mapped_class(model), (
"You need to pass a valid SQLAlchemy Model in " '{}.Meta, received "{}".'
).format(cls.__name__, model)
当转到
is_mapped_class
功能时:(可在:graphene_sqlalchemy/utils.py
)
def is_mapped_class(cls):
try:
class_mapper(cls)
except (ArgumentError, UnmappedClassError):
return False
else:
return True
我在
class_mapper(cls)
处设置了一个断点,该断点打印了实际出错的地方。这与以下事情有关:
sqlalchemy.exc.InvalidRequestError: Mapper 'mapped class Foo->FOO' has no property 'bar'