I have a model
class StudentBasicInfo(models.Model):
usn = models.CharField(blank=False,max_length=10,unique=True,validators=[])
my usn will be in format [0-9][A-Za-z][A-Za-z][0-9][0-9][A-Z][A-Z][0-9][0-9][0-9]
I don't know how to write validation code
create a validator. I'd suggest a RegexValidator like so:
from django.core.validators import RegexValidator
...
class StudentBasicInfo(models.Model):
usn = models.CharField(blank=False,max_length=10,unique=True, validators=[RegexValidator(regex='[0-9][A-Za-z]{2}[0-9]{2}[A-Z]{2}[0-9]{3}', message='Error message goes here')])
I took the liberty of shortening your regex by combining groups that were together. If you want to make the error appear next to the field in the admin you'll have to overload a ModelForm.
Related
How to create ArrayField() in TortoiseORM
from common.base_model import AbstractBaseModel
from tortoise.fields import CharField, BooleanField, ForeignKeyField, ArrayField
class City(AbstractBaseModel):
name = CharField(max_length=100, unique=True)
district = CharField(max_length=100, null=True)
state = CharField(max_length=100)
country = ArrayField() # not working
is_verified = BooleanField(default=True)
There is no ArrayField in TortoiseORM, here is an article about fields in TortoiseORM from its documentation.
As you can see, there is no matching field in TortoiseORM, so you have to extend the existing field class.
I suggest extending the basic class Field because your subclass' to_db_value method has to return the same type as extended field class' to_db_value method, and in the class Field it's not specified.
Next time, try harder - read the documentation and make better questions (add more info, show your attempts).
To achieve the result you want,which I'm assuming is having a field to hold multiple countries, you'd have to create another table for your country field and have a many to many relationship between that table and your city table,its a more conventional implementation that wont have you extend the existing field class.
Suppose I have the following Model:
class myClassObj(models.Model):
flag1 = models.NullBooleanField()
flag2 = models.BooleanField()
Now also suppose I want the Database to enforce the following constraint:
flag1 should be None if and only if flag2 is false
How can I write the constraints in this model so that this condition is checked any time a myClassObj is created or edited? I see some interesting information here. But I don't see how to specify an "iff" constraint as I described above.
The Django documentation recommends doing custom validation where access to multiple fields is required by overriding Model.clean().
This example from the documentation show how it's possible to validate that a news article still in the "draft" phase does not have a publication date.
def clean(self):
import datetime
from django.core.exceptions import ValidationError
# Don't allow draft entries to have a pub_date.
if self.status == 'draft' and self.pub_date is not None:
raise ValidationError('Draft entries may not have a publication date.')
# Set the pub_date for published items if it hasn't been set already.
if self.status == 'published' and self.pub_date is None:
self.pub_date = datetime.date.today()
For more detailed information, see the full reference here: https://docs.djangoproject.com/en/dev/ref/models/instances/#validating-objects
To have this called every time you save the object you'll also need to override the save method: https://docs.djangoproject.com/en/dev/topics/db/models/#overriding-model-methods.
Another useful reference for other use cases if you only need to validate a single field is writing custom validators: https://docs.djangoproject.com/en/dev/ref/validators/
I am trying to achieve a category model where name has unique=True,
but practically I can still add same category name with different cases.
i.e. I have a category called Food
I am still able to add food, FOOD, fOod, FOOd
Is their any philosophy behind this? or it is a work in progress.
Cause in real world if I think of Category Food, it will always be food, no matter what case it has used to mention itself.
Thank you in advance to look at this.
To answer my own question:
I have found I can have clean method on my model. So I added
class Category(models.Model):
name = models.CharField(max_length=200, unique=True)
def clean(self):
self.name = self.name.capitalize()
It is capitalising the first letter, which is then handled by the save method, which calls the validate_unique method to raise error.
You can use Postgre specific model field called Citext fields (case insensitive fields).
There are three option at the moment:
class CICharField(**options), class CIEmailField(**options) and class CITextField(**options)
Example:
from django.db import models
from django.contrib.postgres.fields import CICharField
class Category(models.Model):
name = CICharField(verbose_name="Name", max_length=255)
But don't forget to create an extension for the citext fields.
See here.
Basically, you have to add the extension class in the migration file, inside the operations array, before the first CreateModel operation.
# migration file
operations = [
CITextExtension(), # <------ here
migrations.CreateModel(
...
),
...,
]
Setting the column to case-insensitive collation should fix this. You may need to do it at the SQL level.
I want to implement some kind of tagging functionality to my app. I want to do something like...
class Item(db.Model):
name = db.StringProperty()
tags = db.ListProperty(str)
Suppose I get a search that have 2 or more tags. Eg. "restaurant" and "mexican".
Now, I want to get Items that have ALL, in this case 2, given tags.
How do I do that? Or is there a better way to implement what I want?
I believe you want tags to be stored as 'db.ListProperty(db.Category)' and then query them with something like:
return db.Query(Item)\
.filter('tags = ', expected_tag1)\
.filter('tags = ', expected_tag2)\
.order('name')\
.fetch(256)
(Unfortunately I can't find any good documentation for the db.Category type. So I cannot definitively say this is the right way to go.) Also note, that in order to create a db.Category you need to use:
new_item.tags.append(db.Category(unicode(new_tag_text)))
use db.ListProperty(db.Key) instead,which stores a list of entity's keys.
models:
class Profile(db.Model):
data_list=db.ListProperty(db.Key)
class Data(db.Model):
name=db.StringProperty()
views:
prof=Profile()
data=Data.gql("")#The Data entities you want to fetch
for data in data:
prof.data_list.append(data)
/// Here data_list stores the keys of Data entity
Data.get(prof.data_list) will get all the Data entities whose key are in the data_list attribute
Getting an error with my admin.py file:
'BaseAdmin.fieldsets[1][1]['fields']' refers to field 'publish_on' that is missing from the form.
my class looks like:
class Base(models.Model):
...
publish_on = models.DateTimeField(auto_now=True, db_index=True)
...
My admin.py looks like:
class BaseAdmin(admin.ModelAdmin):
...
fieldsets = [
('Dates', {
'fields': ('publish_on',)
}),
]
if I change out my admin class with 'pass' or just register with the model class then the date time field shows up.
This error is caused by auto_now and also by auto_now_add. To remedy that add
readonly_fields = ("publish_on",)
in your BaseAdmin (only in django 1.2 and newer).
If you do want to use auto_now_add, but then leave open the possibility of changing the date, you could use default=datetime.now in the model field. This sets a default in the admin, but lets the user change it, and it works in inlines.