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Updated docs regarding ReferenceFields

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Closes #149
This commit is contained in:
Ross Lawley 2011-05-25 12:01:41 +01:00
parent 60c8254f58
commit b1cdd1eb26
2 changed files with 30 additions and 0 deletions
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15
docs/tutorial.rst
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@ -152,6 +152,21 @@ We can then store a list of comment documents in our post document::
tags = ListField(StringField(max_length=30)) tags = ListField(StringField(max_length=30))
comments = ListField(EmbeddedDocumentField(Comment)) comments = ListField(EmbeddedDocumentField(Comment))
Handling deletions of references
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
The :class:`~mongoengine.ReferenceField` object takes a keyword
`reverse_delete_rule` for handling deletion rules if the reference is deleted.
To delete all the posts if a user is deleted set the rule::
class Post(Document):
title = StringField(max_length=120, required=True)
author = ReferenceField(User, reverse_delete_rule=CASCADE)
tags = ListField(StringField(max_length=30))
comments = ListField(EmbeddedDocumentField(Comment))
See :class:`~mongoengine.ReferenceField` for more information.
Adding data to our Tumblelog Adding data to our Tumblelog
============================ ============================
Now that we've defined how our documents will be structured, let's start adding Now that we've defined how our documents will be structured, let's start adding

15
mongoengine/fields.py
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@ -555,9 +555,24 @@ class MapField(BaseField):
class ReferenceField(BaseField): class ReferenceField(BaseField):
"""A reference to a document that will be automatically dereferenced on """A reference to a document that will be automatically dereferenced on
access (lazily). access (lazily).
Use the `reverse_delete_rule` to handle what should happen if the document
the field is referencing is deleted.
The options are:
* DO_NOTHING - don't do anything (default).
* NULLIFY - Updates the reference to null.
* CASCADE - Deletes the documents associated with the reference.
* DENY - Prevent the deletion of the reference object.
""" """
def __init__(self, document_type, reverse_delete_rule=DO_NOTHING, **kwargs): def __init__(self, document_type, reverse_delete_rule=DO_NOTHING, **kwargs):
"""Initialises the Reference Field.
:param reverse_delete_rule: Determines what to do when the referring
object is deleted
"""
if not isinstance(document_type, basestring): if not isinstance(document_type, basestring):
if not issubclass(document_type, (Document, basestring)): if not issubclass(document_type, (Document, basestring)):
raise ValidationError('Argument to ReferenceField constructor ' raise ValidationError('Argument to ReferenceField constructor '