Re: Best way to validate a Field at Model level

On 23/01/2014 10:23pm, parnigot wrote:
> Thanks Mike,
>
> Il giorno 23/gen/2014, alle ore 09:16, Mike Dewhirst
> <miked@dewhirst.com.au <mailto:miked@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:

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.
>
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