Up to now the validation/cleaning of a attribute can not access the
value of an other attribute.
The work around is to override the clean() method of the form/model.
A team mate and I talked about it, and we asked ourself, if
a two phase cleaning would help here.
Our idea:
- The first clean phase works like the current implementation
- The second clean phase is optional and does nothing except the user
implements it.
- In the second clean phase your are allowed to peek into
the results of the first clean phase.
The clean method for the second phase would need to get the other values
passed in.
I would like to have this on model level, not only for forms.
Example:
class Issue(models.Model):
state=models.CharField(choices=[('in_progress', 'In progress'),
('wait_until_due_date', 'Wait until due date')])
due_date=models.DateField(null=True)
We want to implement this constraint:
- due date must be set, if the state is "wait_until_due_date".
- due date must not be set, if state is different from "wait_until_due_date".
We know that we can use the clean() method of the model, but a field based
solution would
be more preferred.
class Issue(models.Model):
state = models.CharField(choices=[('in_progress', 'In progress'),
('wait_until_due_date', 'Wait until due date')])
due_date = models.DateField(null=True,
validators2=[check_state_and_due_date_match])
def check_state_and_due_date_match(due_date, all_fields):
state = all_fields['state']
if due_date:
if state != 'wait_until_due_date':
raise ValidationError('If due date is set, state must be
"wait_until_due_date"')
return
if state != 'wait_until_due_date':
raise ValidationError('If no due date is set, state must be
"wait_until_due_date")
Open questions: I am unsure if this should be used only for validation, or if
it should be possible
to alter values, too.
What do you think?
Other solutions or improvements?
Regards,
Thomas Güttler
--
Thomas Güttler
http://thomas-guettler.de/
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