Django, unique time interval for the admin panel
Greetings, Assume I have such model:
class Foo(models.Model):
type = models.ForeignKey(Type)
start_time = models.DateTimeField()
end_time models.DateTimeField()
For each Foo object that is having the same type, I need this time interval (end_time - start_time) to be unique so that 开发者_如何学Pythoncreation of a second Foo with a clashing interval won't be possible. How can this be achieved ?
See the documentation about custom validation in the admin interface.
Basically you have to create your own (model) form, lets say CustomFooAdminForm
and assign it to the admin model:
class FooAdmin(admin.ModelAdmin):
form = CustomFooAdminForm
and in the form you can have something like (see custom validation in forms):
# more or less pseudo code
class CustomFooAdminForm(forms.ModelForm):
def clean(self):
cleaned_data = super(CustomFooAdminForm, self).clean()
interval = cleaned_data.get("end_time") - cleaned_data.get("start_time")
type = cleaned_data.get("type")
q = Foo.objects.extra(select={'interval':'time_end - time_start'}
counter = q.filter(interval=intervak, type=type).count()
if counter > 0:
raise forms.ValidationError("ERROR!!!!")
# Always return the full collection of cleaned data.
return cleaned_data
Maybe you have to transform the DateTimeField
s to UNIX timestamps, before you can subtract them in SQL (UNIX_TIMESTAMP(time_end) - UNIX_TIMESTAMP (time_start)
for MySQL). Or you can use DATEDIFF()
in MySQL to get the difference. But note that you tie your application to a certain database if you use such special functions (as long as they are not available in other databases under the same name).
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