Django - preventing duplicate records - django

Question

I have a list of client records in my database. Every year, we generate a single work order for each client. Then, for each work order record, the user should be able to create a note that is specific to the work order. However, not all work orders need a note, just some.
Now, I can't simply add a note field to the work order because some times, we need to create the note before the work order is even generated. Sometimes this note is specific to a work order that won't happen for 2-3 years. Thus, the notes and the work order must be independent, although they will "find" each other when they both exist.
OK, so here's the situation. I want the user to be able to fill out a very simple note form, where they have two fields: noteYear and note. Thus, all they do is pick a year, and then write the note. The kicker is that the user should not be able to create two notes for the same year for the same client.
What I'm trying to get as is validating the note by ensuring that there isn't already a note for that year for that client. I'm assuming this would be achieved by a custom is_valid method within the form, but I can't figure out how to go about doing that.
This is what I tried so far (note that I know it's wrong, it doesn't work, but it's my attempt so far):
Note that systemID is my client record
My model:
class su_note(models.Model):
YEAR_CHOICES = (
('2013', 2013),
('2014', 2014),
('2015', 2015),
('2016', 2016),
('2017', 2017),
('2018', 2018),
('2019', 2019),
('2020', 2020),
('2021', 2021),
('2022', 2022),
('2023', 2023),
)
noteYear = models.CharField(choices = YEAR_CHOICES, max_length = 4, verbose_name = 'Relevant Year')
systemID = models.ForeignKey(System, verbose_name = 'System ID')
note = models.TextField(verbose_name = "Note")
def __unicode__(self):
return u'%s | %s | %s' % (self.systemID.systemID, self.noteYear, self.noteType)
And my form:
class SU_Note_Form(ModelForm):
class Meta:
model = su_note
fields = ('noteYear', 'noteType', 'note')
def is_valid(self):
valid = super (SU_Note_Form, self).is_valid()
#If it is not valid, we're done -- send it back to the user to correct errors
if not valid:
return valid
# now to check that there is only one record of SU for the system
sysID = self.cleaned_data['systemID']
sysID = sysID.systemID
snotes = su_note.objects.filter(noteYear = self.cleaned_data['noteYear'])
for s in snotes:
if s.systemID == self.systemID:
self._errors['Validation_Error'] = 'There is already a startup note for this year'
return False
return True
EDIT -- Here's my solution (thanks to janos for sending me in the right direction)
My final form looks like this:
class SU_Note_Form(ModelForm):
class Meta:
model = su_note
fields = ('systemID', 'noteYear', 'noteType', 'note')
def clean(self):
cleaned_data = super(SU_Note_Form, self).clean()
sysID = cleaned_data['systemID']
sysID = sysID.systemID
try:
s = su_note.objects.get(noteYear = cleaned_data['noteYear'], systemID__systemID = sysID)
print(s)
self.errors['noteYear'] = "There is already a note for this year."
except:
pass
return cleaned_data
For anyone else looking at this code, the only confusing part is the line that has: sysID = sysID.systemID. The systemID is actually a field of another model - even though systemID is also a field of this model -- poor design, probably, but it works.

Answer 1

See this page in the Django docs:
https://docs.djangoproject.com/en/dev/ref/forms/validation/
Since your validation logic depends on two fields (the year and the systemID), you need to implement this using a custom cleaning method on the form, for example:
def clean(self):
cleaned_data = super(SU_Note_Form, self).clean()
sysID = cleaned_data['systemID']
sysID = sysID.systemID
try:
su_note.objects.get(noteYear=cleaned_data['noteYear'], systemID=systemID)
raise forms.ValidationError('There is already a startup note for this year')
except su_note.DoesNotExist:
pass
# Always return the full collection of cleaned data.
return cleaned_data