FixedCharField is used similarly to CharField, but takes a length attribute, and will only accept strings with that exact length.
class Student(models.Model):
student_id = FixedCharField(length=8)
It currently only supports mysql, sqlite3, and oracle. The port to postgresql should be straightforward but I'm not sure about it so I haven't added it yet.
This is a copy-paste (plus a couple of adaptations) from my project Chango, found at http://launchpad.net/chango/, so in order to keep up with latest updates it might be a good idea to use code directly from there.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 | ############################
## This goes in forms.py ##
############################
from django import forms
from django.utils.translation import ugettext_lazy as _
from django.forms.util import ValidationError
from django.forms.widgets import TextInput, PasswordInput
class FixedCharField(forms.CharField):
default_error_messages = {
'wrong_length': _(u'Ensure this value has exactly %(set_length)d characters (it has %(value_length)d).'),
}
def __init__(self, length, *args, **kwargs):
self.length = length
super(FixedCharField, self).__init__(*args, **kwargs)
def clean(self, value):
"Validates length. Returns a Unicode object."
value = super(FixedCharField, self).clean(value)
value_length = len(value)
if value_length != self.length:
raise ValidationError(self.error_messages['wrong_length'] % {'set_length': self.length, 'value_length': value_length})
return value
def widget_attrs(self, widget):
if isinstance(widget, (TextInput, PasswordInput)):
# The HTML attribute is maxlength, not max_length.
return {'maxlength': str(self.length)}
############################
## This goes in models.py ##
############################
from myapp.forms import FixedCharField as FixedCharFormField
from django.db import models
from django.db import connection
from django.conf import settings
from django.utils.datastructures import DictWrapper
class FixedCharField(models.Field):
def __init__(self, verbose_name=None, name=None, primary_key=False,
length=None, *args, **kwargs):
if length == None:
raise Exception("FixedCharField needs length attribute.")
self.length = length
# The kwargs will never include verbose_name nor name. (TODO: Really?)
kwargs['verbose_name'] = verbose_name
kwargs['name'] = name
super(FixedCharField, self).__init__(*args, **kwargs)
def db_type(self):
data = DictWrapper(self.__dict__, connection.ops.quote_name, "qn_")
if settings.DATABASE_ENGINE == 'mysql':
return 'char(%(length)s)' % data
elif settings.DATABASE_ENGINE == 'sqlite3':
return 'char(%(length)s)' % data
elif settings.DATABASE_ENGINE == 'oracle':
return 'VARCHAR2(%(length)s)' % data
else:
return models.CharField.db_type(self)
# def get_internal_type(self):
# return "FixedCharField"
def to_python(self, value):
return models.CharField(self, value)
def formfield(self, **kwargs):
defaults = {'form_class': FixedCharFormField,
'length': self.length}
defaults.update(kwargs)
return super(FixedCharField, self).formfield(**defaults)
|
More like this
- Template tag - list punctuation for a list of items by shapiromatron 10 months, 3 weeks ago
- JSONRequestMiddleware adds a .json() method to your HttpRequests by cdcarter 11 months ago
- Serializer factory with Django Rest Framework by julio 1 year, 5 months ago
- Image compression before saving the new model / work with JPG, PNG by Schleidens 1 year, 6 months ago
- Help text hyperlinks by sa2812 1 year, 7 months ago
Comments
How does this differ from using a CharField with a max_length and min_length of equal value?
#
Oh it appears only forms.CharField has a min_length argument. db.models.CharField does not.
#
Please login first before commenting.