How to customize Django model's field.value_to_string(self) for datetime field

Question

Let's say I have a model

class Job(Model):
     created_on = DateTimeField(_("Created On"), auto_now=True, editable=False)
     name = CharField(_("Name"), max_length=300, blank=False)

Now I am trying to aggregate all fields with their verbose name and value to display it in a template.

My aggregating function:

def get_fields(self):
    result = []
    for field in Job._meta.fields:
        result.append((field.name, field.verbose_name, field.value_to_string(self)))

This gives me the values as string properly, however for a datetime field, I end up with a dumb unformatted string like 2021-02-13T22:39:47.561045+00:00 I really don't want to check and modify the value in some way by specifically checking for the particular field as that is the whole point of my get_field function

I feel any of the following should work fine for me:

Somehow provide the default format to use when calling value_to_string()
Get a proper dateTime object instead, in which case the value should show up fine on the template
Get field type and then instead of calling value_to_string() I manually convert the string to this type (This seems feasible from what I see but feels too hacky of a solution)

SDRJ · Accepted Answer · 2021-02-14T21:07:13.967

1

@L Lawliet- Does something like this work. You can add it as models method.

def get_formatted_date(self):
        return self.created_on.strftime("%Y-%m-%d %H:%M:%S")

Alternative approach - source Formatting DateTimeField in Django

class CustomDateTimeField(models.DateTimeField):
    def value_to_string(self, obj):
        val = self.value_from_object(obj)
        if val:
            val.replace(microsecond=0)
            return val.isoformat()
        return ''

in your model

   created_on = CustomDateTimeField(auto_now_add=True)

edited Feb 14 '21 at 21:07

answered Feb 14 '21 at 21:00

SDRJ

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3
11

Well if I define it as a property, I can sort of get it to work but the problem is that if I do that, in my aggregation function, I have to make an exception specifically for that field which is what I am trying to avoid :( – L Lawliet Feb 14 '21 at 21:03
@LLawliet- I have made some edit. Can you try and see if that works? – SDRJ Feb 14 '21 at 21:07
Thanks. Apparently basic field.value_from_object(self) works for my case, but for getting a custom format by default, this seems ideal! – L Lawliet Feb 14 '21 at 21:12

score 1 · Answer 2 · answered Feb 14 '21 at 21:10

Here is what worked for me:

field.value_from_object(self)

instead of

field.value_to_string(self)

The advantage is the return value is an object which is solution(2) for me. In this case since the object is of the proper type, it got displayed properly!

How to customize Django model's field.value_to_string(self) for datetime field

2 Answers2