[MongoMapper] Remove an attribute

[jmonteiro]

Hello,

I would like to remove an attribute from an object saved as a
MongoMapper::Document.

In the MongoDB Developer FAQ (http://www.mongodb.org/display/DOCS/
Developer+FAQ), there is the following statement:

> If you remove an object attribute is it deleted from the store?
> Yes, you remove the attribute and then re-save() the object.

Thank you,
Julio

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[Andrew Timberlake]

You can use obj.unset(:key_name)

Andrew Timberlake
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[John Nunemaker]

I absolutely love that you all answer before I can. Saves me a lot of work. Thanks for helping out on the list everyone!

[John Nunemaker]

One addition, you can also remove a key from all fields like this:

Foo.unset({}, :some_key)

Or just those that match particular criteria:

Foo.unset({:tags => 'red'}, :some_key)

On Fri, Apr 30, 2010 at 5:05 AM, Andrew Timberlake <and...@andrewtimberlake.com> wrote:

[Adilson Chacon]

"unset" works for Joint too?

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[John Nunemaker]

Yeah, it could. You would need to do it for each of the 4 keys and then would also want to remove the files from GridFS.

[Adilson Chacon]

OK, thanks!

[Dan Gal]

how to unset from embedded document? it doesn't seem to work...

[Jamie Orchard-Hays]

Should just be

parent_model_instance.unset("path.to.embedded_attr").

Or just drop to the driver:

ParentModel.collection.update({your query}, {:$unset => {"path.to.embedded_attr" => true}})

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[Dan Gal]

Thanks for the quick reply but my embedded document is of type 'many' (array). 

for example I have the parent 'package' which has an embedded document of type many named 'page'. How do I unset one of pages fields?

[Jamie Orchard-Hays]

You will have to drop to the driver for doing this in an embedded array. Check the mongodb docs on Arrays. I think there's a way to find the position of the doc in the Array and then alter values. It may take some digging around and experimenting.