Add possibility to update a document or a whole query from JSON

[cod3monk]

We already have to_json() and from_json(data), but the later only creates a whole new Document. My problem is, that I need to update only certain fields and the document is already loaded.

It would be nice to be able to load a partial json representation of a Document and only update the passed fields.

Example:

>>> class Test(Document):
...     name = StringField()
...     foo = StringField(default="bar")
...
>>> t = Test()
>>> t.save()
<Test: Test object>
>>> t.to_json()
'{"_id": {"$oid": "5198cf4759055e1762366812"}, "foo": "bar"}'
>>> t.from_json('{"name": "Baz!"}', update_inplace=True)
<Test: Test object>
>>> t.name
u'Baz!'

Here from_json with update_inplace=True would return self and not a new Test object.

Alternatively an update_from_json function could do the same.

[takbir]

It's what I need now, it'll be nice !

[snario]

+1

[Taik]

+1, would be really nice.

[ben-maystreet]

Too bad we don't have this yet, I really need to use this function!!!

[mmellison]

Is there a reason why you can't just json.loads the JSON and call update? I agree this would be nice to hide the "magic" inside MongoEngine, but does that not work as a suitable work around for now?

Off the top of my head:

t = Test()
t.update(**json.loads('{"name": "Baz!"}'))

[subodhpareek18]

+1 for this
@seglberg the method you're suggesting, do you think it'll work for nested json? Since that's the hard requirement.

t = Test()
t.update(**json.loads('{"contact":{"name": "Baz!"}}'))

[wojcikstefan]

Quick iPython test shows that it works w/ embedded documents and lists:

In [24]: class Role(EmbeddedDocument):
    role = StringField()
   ....:

In [25]: class User(Document):
    name = StringField()
    roles = ListField(EmbeddedDocumentField(Role))
   ....:

In [26]: u = User(name='Jack', roles=[Role(role='nbc'), Role(role='microwaves')]).save()

In [27]: data = {'roles': [{'role': 'nbc'}]}

In [28]: u.update(**data)
Out[28]: 1

In [29]: u.reload()
Out[29]: <User: User object>

In [30]: u.roles
Out[30]: [<Role: Role object>]

In [31]: u.roles[0].role
Out[31]: u'nbc'

[hirodeng]

@wojcikstefan Your solution seems right, but it seems strange to me that the update method updates the document in the database directly, so you use reload to update the python object after that. This is different to what the from_json method do, which modifies the python object first and then save() to the database. What I am looking for is a method that also modifies the python object first and then update the database. It makes creating and updating operations more unified.