Best way to validate a Field at Model level

[parnigot]

Hi,

In my models I’ve some FloatFields that must be > 0. I’m wondering what is the best way to check, at the model level (not form), that the values for these Fields are greater than 0? Browsing the documentation I’ve found the following three methods:

• Add the MinValueValidator to each field.
• Check them in the model.clean() method
• Create a custom field that accept only floats > 0.

And, if a choose the custom field, which FloatField’s method do I need to override to check that the value is > 0?

Best regards,

e.p.

[Mike Dewhirst]

On 23/01/2014 7:03pm, parnigot wrote:
> Hi,
>
> In my models I’ve some FloatFields that must be > 0. I’m wondering what
> is the best way to check, at the model level (not form), that the values
> for these Fields are greater than 0? Browsing the documentation I’ve
> found the following three methods:
>

> * Add the MinValueValidator
> <https://docs.djangoproject.com/en/1.6/ref/validators/#minvaluevalidator> to
> each field.
> * Check them in the model.clean() method

I use the model's clean() method which is always called by the form.
However, if you are not using forms you have to remember to call the
clean method. Eg, in unit tests.

> * Create a custom field that accept only floats > 0.

>
>
> And, if a choose the custom field, which FloatField’s method do I need
> to override to check that the value is > 0?

I don't use floats as a rule but I would probably use isinstance and
possibly a range like > -0.000001 and < 0.000001 or whatever your app
requires.

mike

>
> Best regards,
> e.p.
>
> --
> You received this message because you are subscribed to the Google
> Groups "Django users" group.
> To unsubscribe from this group and stop receiving emails from it, send
> an email to django-users...@googlegroups.com.
> To post to this group, send email to django...@googlegroups.com.
> Visit this group at http://groups.google.com/group/django-users.
> To view this discussion on the web visit
> https://groups.google.com/d/msgid/django-users/DDD1702B-CA41-4A8B-94DC-76C8D6B39EDD%40gmail.com.
> For more options, visit https://groups.google.com/groups/opt_out.

[parnigot]

Thanks Mike,

Il giorno 23/gen/2014, alle ore 09:16, Mike Dewhirst <mi...@dewhirst.com.au> ha scritto:

On 23/01/2014 7:03pm, parnigot wrote:

Hi,

In my models I’ve some FloatFields that must be > 0. I’m wondering what
is the best way to check, at the model level (not form), that the values
for these Fields are greater than 0? Browsing the documentation I’ve
found the following three methods:

 * Add the MinValueValidator
   <https://docs.djangoproject.com/en/1.6/ref/validators/#minvaluevalidator> to
   each field.
 * Check them in the model.clean() method

I use the model's clean() method which is always called by the form. However, if you are not using forms you have to remember to call the clean method. Eg, in unit tests.

What about the MinValueValidator and the custom field. Do they validate automatically only with forms like model.clean() or they raise ValidationError even with a model.save()?

 * Create a custom field that accept only floats > 0.


And, if a choose the custom field, which FloatField’s method do I need
to override to check that the value is > 0?

I don't use floats as a rule but I would probably use isinstance and possibly a range like > -0.000001 and < 0.000001 or whatever your app requires.

Ok, thanks for reminding me that. But my original question was in which method of my PositiveCustomField I need to put the logic to check if the value is valid:

if value <= 0:

raise ValidationError(“value must be > 0”)

Best regards,

e.p.

[Mike Dewhirst]

On 23/01/2014 10:23pm, parnigot wrote:
> Thanks Mike,
>
> Il giorno 23/gen/2014, alle ore 09:16, Mike Dewhirst

> <mi...@dewhirst.com.au <mailto:mi...@dewhirst.com.au>> ha scritto:

Honestly, I have only ever used one custom field and eventually ripped
it out because the non-standard-ness added to the maintenance load.

So I'm not the right person to answer that one ...

Sorry

Mike

>
> if value <= 0:
> raise ValidationError(“value must be > 0”)
>
> Best regards,
> e.p.
>

> --
> You received this message because you are subscribed to the Google
> Groups "Django users" group.
> To unsubscribe from this group and stop receiving emails from it, send
> an email to django-users...@googlegroups.com.
> To post to this group, send email to django...@googlegroups.com.
> Visit this group at http://groups.google.com/group/django-users.
> To view this discussion on the web visit

> https://groups.google.com/d/msgid/django-users/C1F789C3-0CE8-4333-9465-0255234A6EAD%40gmail.com.