save() method could return the object

[Chris Wilson]

Hi all,

If the save() method returned the object itself, then we could chain it
like this:

old_status = Status(last_contact=None).save()

Instead of having to do this:

old_status = Status(last_contact=None)
old_status.save()

It's a trivial one-line change to the Model class and I don't think it
would break backwards compatibility, as I doubt that anyone is relying on
the save() method returning None. Should I submit a patch?

Cheers, Chris.
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[David Winterbottom]

While such a change is initially appealing, it violates the command-query separation principle in that a 'command' method such as 'save' should not return anything. 

http://en.wikipedia.org/wiki/Command-query_separation

Hence, it's not a good idea to make this change.  It's more important to have clearly purposed methods than saving a line of code.

David

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[Marijonas Petrauskas]

There already exists create method that does exactly what you need:

obj = SomeModel.objects.create(name='foo', age=42)

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[Yo-Yo Ma]

+1

A lot of people are overriding ``save`` and not returning anything, but this isn't going to hurt them (ideally, they should already be returning the result of ``super(``, but nobody does).

[Alex Gaynor]

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This isn't going to happen. It violates a fundamental API design in Python: methods which mutate/have side effects return none, methods which return a new object... return a new object. This has a side effect, and doesn't construct a new object, ergo, it returns None.

Alex

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[Chris Wilson]

On Fri, 12 Oct 2012, Marijonas Petrauskas wrote:

> There already exists create method that does exactly what you need:obj = SomeModel.objects.create(name='foo', age=42)

OK, thanks, that appears to be completely undocumented.

[Alex Gaynor]

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https://docs.djangoproject.com/en/1.4/ref/models/querysets/#create