MongoEngine ValidationError

Question

我必须创建一个数据库，以及如何检查是否所有条目都被输入到数据库中，或者没有使用python。

我写了一个叫做审判的课

class Trial(db.Document):
    project_name = db.StringField(max_length=255,required=True)
    list_of_materials = db.ListField(db.EmbeddedDocumentField('List_Of_Materials'))
    abstract = db.StringField(max_length=255,required=True)
    vehicle = db.StringField(max_length=255,required=False)
    responsibilities = db.ListField(db.EmbeddedDocumentField('Responsibilities')) 

我将类List_of_Materials和职责定义为：

class Responsibilities(db.EmbeddedDocument):
    employee = db.StringField(max_length=255, required = True)
    objective = db.StringField(max_length=255, required = True)

class List_Of_Materials(db.EmbeddedDocument):
    mat_name = db.StringField(max_length=255, required=True)
    mat_type = db.StringField()
    mat_comments = db.StringField(max_length = 255)

现在，我使用python向数据库输入一个条目。

trial_test = Trial(project_name = 'nio field trip management',
                list_of_materials = [List_Of_Materials(mat_name = 'Laptop')],
                abstract = 'All is well that ends well',
                vehicle = Vehicle(veh_name='My Laptop',veh_num='GA07EX1234'),
                responsibilities = [Responsibilities(employee='Prashant',objective='Setup the Website')],

我得到了以下错误：

Traceback (most recent call last):
  File "<stdin>", line 12, in <module>
  File "C:\Anaconda\lib\site-packages\mongoengine\base\document.py", line 85, in __init__
    value = field.to_python(value)
  File "C:\Anaconda\lib\site-packages\mongoengine\base\fields.py", line 261, in to_python
    self.error('You can only reference documents once they'
  File "C:\Anaconda\lib\site-packages\mongoengine\base\fields.py", line 124, in error
raise ValidationError(message, errors=errors, field_name=field_name)
mongoengine.errors.ValidationError: You can only reference documents once they have been saved to the database

代码的第12行是responsibilities=db.ListField(db.EmbeddedDocumentField('Responsibilities'))

从上面的错误中我可以理解的是，我们必须首先输入类"Responsibilities“和"List_Of_Material”，但是"List_Of_Material“中的条目没有显示任何错误，而"Responsibilities”中的条目显示了上面的错误。

我怎样才能避免这个问题呢？

Answer 1

您确定您发送的Trial模型是正确的吗？

当在文档中声明ReferenceField时，会引发此ReferenceField，但在保存引用文档之前尝试保存此文档(Mongoengine将MongoDB中的引用字段表示为包含引用的类和ObjectId的字典)。

EmbeddedDocumentField不是ReferenceField。它们在保存主文档的同时保存。因此，我不认为您的错误来自list_of_materials或responsibilities属性。如果在示例中删除车辆分配，则此代码运行良好。

考虑到您的代码示例，我猜有一个类类似

class Vehicle(db.Document):
    veh_name = db.StringField()
    veh_num = db.StringField()

你的模型是：

class Trial(db.Document):
    project_name = db.StringField(max_length=255, required=True)
    list_of_materials = db.ListField(db.EmbeddedDocumentField('List_Of_Materials'))
    abstract = db.StringField(max_length=255, required=True)
    vehicle = db.ReferenceField(Vehicle)
    responsibilities = db.ListField(db.EmbeddedDocumentField('Responsibilities'))

然后，你的例子应该是：

trial_test = Trial(
     project_name = 'nio field trip management',
     list_of_materials = [List_Of_Materials(mat_name = 'Laptop')],
     abstract = 'All is well that ends well',
     vehicle = Vehicle(veh_name='My Laptop',veh_num='GA07EX1234'),
     responsibilities = [Responsibilities(employee='Prashant',objective='Setup the Website')]
)
trial_test.vehicle.save()  # Saving the reference BEFORE saving the trial.
trial_test.save()