So I've got a UserProfile in Django that has certain fields that are required by the entire project - birthday, residence, etc. - and it also contains a lot of information that doesn't actually have any importance as far as logic goes - hometown, about me, etc. I'm trying to make my project a bit more flexible and applicable to more situations than my own, and I'd like to make it so that administrators of a project instance can add any fields they like to a UserProfile without having to directly modify the model. That is, I'd like an administrator of a new instance to be able to create new attributes of a user on the fly based on their specific needs. Due to the nature of the ORM, is this possible?
Well a simple solution is to create a new model called UserAttribute that has a key and a value, and link it to the UserProfile. Then you can use it as an inline in the django-admin. This would allow you to add as many new attributes to a UserProfile as you like, all through the admin:
models.py
class UserAttribute(models.Model):
key = models.CharField(max_length=100, help_text="i.e. Age, Name etc")
value = models.TextField(max_length=1000)
profile = models.ForeignKey(UserProfile)
admin.py
class UserAttributeInline(admin.StackedInline):
model = UserAttribute
class UserProfile(admin.ModelAdmin):
inlines = [UserAttibuteInline,]
This would allow an administrator to add a long list of attributes. The limitations are that you cant's do any validation on the input(outside of making sure that it's valid text), you are also limited to attributes that can be described in plain english (i.e. you won't be able to perform much login on them) and you won't really be able to compare attributes between UserProfiles (without a lot of Database hits anyway)
You can store additional data in serialized state. This can save you some DB hits and simplify your database structure a bit. May be the best option if you plan to use the data just for display purposes.
Example implementation (not tested)::
import yaml
from django.db import models
class UserProfile(models.Model):
user = models.OneToOneField('auth.User', related_name='profile')
_additional_info = models.TextField(default="", blank=True)
#property
def additional_info(self):
return yaml.load(self._additional_info)
#additional_info.setter
def additional_info(self, user_info_dict):
self._additional_info = yaml.dump(user_info_dict)
When you assign to profile.additional_info, say, a dictionary, it gets serialized and stored in _additional_info instead (don't forget to save the instance later). And then, when you access additional_info, you get that python dictionary.
I guess, you can also write a custom field to deal with this.
UPDATE (based on your comment):
So it appears that the actual problem here is how to automatically create and validate forms for user profiles. (It remains regardless on whether you go with serialized options or complex data structure.)
And since you can create dynamic forms without much trouble[1], then the main question is how to validate them.
Thinking about it... Administrator will have to specify validators (or field type) for each custom field anyway, right? So you'll need some kind of a configuration option—say,
CUSTOM_PROFILE_FIELDS = (
{
'name': 'user_ip',
'validators': ['django.core.validators.validate_ipv4_address'],
},
)
And then, when you're initializing the form, you define fields with their validators according to this setting.
[1] See also this post by Jacob Kaplan-Moss on dynamic form generation. It doesn't deal with validation, though.
Related
Here is my models.py:
class Item(models.Model):
# ... some irrelevent fields ...
tags = models.ManyToManyField('Tag')
class Tag(models.Model):
name = models.CharField(max_lenght=30)
category_id = models.IntegerField()
Tag is actually a general-purpose name. Each item has many different type of tags - currently there are four types: team tags, subject tags, admin tags and special tags. eventually there will probably be a few more.
The idea is, they all have basically the same fields, so instead of having like 4 tables with manytomany relationship, and instead of adding a new column for Item whenever adding a new type, everything is called a 'tag' and it's very easy to add new types without any change to the schema.
Now to handle this in the admin.py I'm using dyamically created proxy models (based on this), as such:
def create_modeladmin(modeladmin, model, name = None):
class Meta:
proxy = True
app_label = model._meta.app_label
attrs = {'__module__': '', 'Meta': Meta}
newmodel = type(name, (model,), attrs)
admin.site.register(newmodel, modeladmin)
return modeladmin
class TagAdmin(models.Model):
def queryset(self):
return self.model.objects.filter(category_id = self.cid)
class TeamAdmin(TagAdmin):
cid = 1
class SubjectAdmin(TagAdmin):
cid = 2
# ... and so on ...
create_modeladmin(TeamAdmin, name='Teams', model=Tag)
create_modeladmin(SubjectAdmin, name='Subject', model=Tag)
#... and so on ...
This works great for me. However, different staff members need different editing permissions - one guy shouldn't access admin tags, while the other should only have access to edit subject-tags and team-tags. But as far as the admin site is concerned - the dynamic models do not exist in the permission list, and I can't give anyone permissions regarding them.
i.e. a user given all permissions on the list will still not have access to edit any of the dynamic models, and the only way to let anyone access them at all is to give him a superuser which obviously defies the point
I searched SO and the web and I can't anyone with a similar problem, and the docs don't say anything about this not in the dynamic models section or the proxy models section. so I'm guessing this is a different kind of problem. Any help would be greatly appreciated
UPDATE
So after some research into it, the answer was simple enough. Since permissions in django are objects that are saved to the database, what I needed to do was simple - add the relevent permissions (and create new ContentType objects as well) to the db, and then I could give people specific pemissions.
However, this raised a new question - is it a good convention to put the function that creates the permissions inside create_modeladmin as a find_or_create sort of function (that basically runs every time) or should it be used as an external script that I should run once every time I add a new dynamic model (sort of like how syncdb does it)?
And is there a way to also create the permissions dynamically (which seems to me like the ideal and most fitting solution)?
of course you can create permissions, django have django.contrib.auth.management.create_permissions to do this
Right now I'm using Django's built in admin system to manage users, to which I've attached a profile to contain additional data using the following:
class Profile(models.Model):
user = models.OneToOneField(User, editable = False)
# Data fields here...
As it stands the User and Profile pk (and accordingly id number) will be the same if and only if the profile is created right after the user is created. I could guarantee that this would be the case during the registration process, and while that would cover most uses, creating users with the admin interface could cause mismatched ids to occur. Thus this does not seem like a very robust way to solve this problem and I'd like to hardcode the pk's to be the same. I'm not sure how to do this.
I thought the following would work:
profile_id = models.IntegerField(default=user.pk, editable = False,
primary_key = True)
But it gives me the error:
AttributeError: 'OneToOneField' has no attribute 'pk'
What's the best way to guarantee that the profile and user have the same pk? Note: I'd really rather not deal with extending the base user model as using the OneToOneField to link the two seems to be sufficient for all my needs.
Thanks!
[edit]
My reasoning for asking the question:
My immediate problem was that I wanted a dictionary of values of the User's Profile, which I was retrieving usingprofile_values = Profile.objects.filter(pk=user.id).values()[0]. This highlighted the bug, and I "hacked" around it last night using pk=user.profile.id instead. In the light of the morning this does not seem like such a terrible hack. However, it seems like having pk discrepancies could lead to quiet and hard to catch bugs down the line, and thus forcing them to match up would be a Good Idea. But I'm new to Django so I'd entirely accept that it is, in fact, never a problem if you're writing your code correctly. That said, for almost academic reasons, I'd be curious to see how this might be solved.
[/edit]
Like you already agree that it was never a problem because we have a OneToOne mapping between the two models.
So when you need to get the profile obj corresponding to a User:
profile_values = Profile.objects.get(user_id=user)
assuming,
class Profile(models.Model):
user = models.OneToOneField(User)
...
If your column name is not user, then use the corresponding name in get query.
Still if you are curious as to how to achieve same pk for both models, then we can set a signal on every save of User model. See the documentation.
def create_profile(sender, **kwargs):
if kwargs["created"]:
p = Profile(user=kwargs["instance"], ...)
p.save()
django.db.models.signals.post_save.connect(create_profile, sender=User)
create_profile() will be called every time any User object is saved.
In this function, we create Profile object only if a new User instance has been created.
If we start from blank slate, then I think this will always make sure that a Profile exists for every User and is created right after User was created; which in turn will give same pk for both models.
pk is a parameter in a filter() query, but not a field name. You probably want to use user.id.
I think this is best explained with some simple model code (I'm writing this from scratch so possible syntax issues - unimportant here):
class Car(models.Model)
make = models.CharField(...)
model = models.CharField(...)
class StatisticType(models.Model):
name = models.CharField(...)
class Statistic(models.Model)
car = models.ForeignKey('Car')
stype = models.ForeignKey('StatisticType')
data = models.CharField(...)
class Meta:
unique_together = (('car', 'stype'),)
We have a car with some hard-coded stats and we have some database controlled statistics. I might add Colours, Wheel Size, etc. The point is it's editable from the admin so neither I or the client need to climb through the data, but it's limited so users can only pick one of each stat (you can't define "Colours" twice).
So I'm trying to write the data input form for this now and I want a list of optional ModelForms that I can chuck on the page. I've got the simplest ModelForm possible:
class StatisticForm(forms.ModelForm):
class Meta:
model = Statistic
The tricky part (in my head) is generating an instance of this ModelForm for each StatisticType, regardless of it existing yet. That is to say if a Car object doesn't have a Colour assigned to it, the form still shows. Similarly, if it does, that instance of a Statistic is loaded in the ModelForm.
In my view, how do I generate a list of these things, regardless of there being a pre-existing instance of any given Statistic?
This seems like it should be a stupidly simple thing to do but it's late on Friday and everything looks skwonky.
Sounds like you might want to leverage an inline model formset factory.
That would allow you to create as many instances of your Statistic object as you need. If you're needing to create instances of your StatisticType on the fly, that's a bit different.
When Django instantiates forms, for a foreign key, m2m or choice field, it will only accept choices that it deems "valid", and will complain if you add a choice using JavaScript that doesn't exist in a related model or set of choices server-side.
So, if you need to make StatisticTypes on the fly, and then populate formset instances with this new value, I would suggest using Knockout.js. It's very good at keeping lots of DOM elements in sync when data changes.
I have a django based web shop that has been evolving over the past year. Currently there's about 8 country specific shops running through the same code base, plus an API, and there's soon to be a B2B website, and a few more countries to add to the list.
Variations are needed in model structure, particularly around fields in address models, the account model, and so on.
To make matters a bit more complicated, the site is running multidb with each shop instance in a separate db. So I have a situation where I might have a base ABC model, e.g:
class Address(models.Model):
class Meta:
abstract=True
class Address_UK(Address):
class Meta:
db_table="shop_address"
class Address_IT(Address):
class Meta:
db_table="shop_address"
[etc]
Then code throughout the app to select the the correct model, e.g.
if countrysettings.country == "UK":
address = Address_UK()
elif countrysettings.country == "IT":
address = Address_IT()
The countrysettings.country is actually a separate settings class which subclasses threading.local and the country code, which also corresponds with a key in settings.DATABASES, is configured by a geolocation middleware handler. So the correct database is selected, and the model specific variations are reflected in each country database.
But there are problems to this approach:
It completely breaks syncdb and is no good for south, unless I hack ./manage.py so I can pass in the country db, instead of requiring the middleware to set it.
It seems messy. So much if countrysettings.country == "xx": code lying about, and so many sub classed models.
So I was thinking of using django-eav instead, but I foresee problems in the admin, and in particular field ordering. I know that django-eav will build a modelform for the admin that includes the eav fields, but I'd ideally want these to be displayed or hidden relevant to the country.
Also I've considered having a none abstract base class, e.g. Address, and then creating country specific variations where needed (e.g Model Table Inheritance). But then I foresee the base models getting overloaded with one2one fields to each model variant. But it would solve issues with the admin.
Another option might be to have an extra data field, and to serialise additional fields into json or csv or something and store them in this field.
I can think about a few others way to attack your problem. I believe option 1 or option 2 are the best, but one might choose option 3.
Option 1: One code base, One db, One django instance, Sites framwork: If you do not actually need a distinct db for each store, create all tables and/or all possible fields, and smartly use the sites framework for condour fields fields and models. For example: keep for each address a address_type field etc and use different fields (and tables) on the same db for each site. This makes your code more complicated but simplifies your IT a lot. Use this if the code changes between sites is very minimal. (btw - The json serialization is a good option for address).
Option2: One code base, Many DBs, Many django instances: Set many sites with the same code base but carefully use conditional settings and dynamic features of python to generate different models per site. Each site will have it's own settings-uk.py, settings-us.py etc., and will have it's own db and own models using dynamic models. For example:
from django.conf import settings
# ...
class Address(models.Model):
name = models.CharField(max_length=100)
if settings.country == "US":
state = models.CharField(max_length=2)
else:
country = models.CharField(max_length=100)
Other possible tricks for this method: Enable/disable apps via the settings; Crafting custom pythonpaths for appsin the wsgi script/manage.py script; use if settings.country=='us': import uk_x as x else: import us_x as x . See also: http://code.flickr.com/blog/2009/12/02/flipping-out/
Option3: Parallel code branches, Many DBs, Many django instances: Use git to keep a few branches of your code and rebase them with each other. Requires much more IT effort. If you are planning to have many db and many server, (and many developers?) anyway, you might find this useful.
Another options: One DB, many django instances custom settings.py per instance without sites framework.
Actually EAV can solve your issue. You can in fact use EAV to show fields that a specific to the country attribute of the current object.
Here is an example
class Country(models.Model):
name = models.CharField(_("country"), max_length=50
class Address(eav.models.BaseEntity):
country = models.ForeignKey(Country, related_name="country_attrs")
# EAV specific staff
#classmethod
def get_schemata_for_model(self):
# When creating object, country field is still not set
# So we do not return any country-specific attributes
return AddressEAVSchema.objects.filter(pk=-1).all()
def get_schemata_for_instance(self, qs):
# For specific instance, return only country-specific attributes if any
try:
return AdressEAVSchema.objects.filter(country=self.country).all()
except:
return qs
# Attributes now can be marked as belonging to specific country
class AdressEAVSchema(eav.models.BaseSchema)
country = models.ForeignKey(Country, related_name="country_attrs")
# Rest of the standard EAV stuff
class AdressEAVChoice(eav.models.BaseChoice):
schema = models.ForeignKey(AdressEAVSchema, related_name='choices')
class AddressEAVAttribute(eav.models.BaseAttribute):
schema = models.ForeignKey(AdressEAVSchema, related_name='attrs')
choice = models.ForeignKey(AdressEAVChoice, blank=True, null=True)
Here how to use it:
When you create Address attributes you now have also to specify which country they belong to.
Now, when you create new Address object itself (say in admin), save, and then go back editing it you see additional country-specific attributes that match objects country.
Hope this helps.
This is a problem concerning django.
I have a model say "Automobiles". This will have some basic fields like "Color","Vehicle Owner Name", "Vehicle Cost".
I want to provide a form where the user can add extra fields depending on the automobile that he is adding. For example, if the user is adding a "Car", he will extra fields in the form, dynamically at run time, like "Car Milage", "Cal Manufacturer".
Suppose if the user wants to add a "Truck", he will add "Load that can be carried", "Permit" etc.
How do I achieve this in django?
There are two questions here:
How to provide a form where the user can add new fields at run time?
How to add the fields to the database so that it can be retrieved/queried later?
There are a few approaches:
key/value model (easy, well supported)
JSON data in a TextField (easy, flexible, can't search/index easily)
Dynamic model definition (not so easy, many hidden problems)
It sounds like you want the last one, but I'm not sure it's the best for you. Django is very easy to change/update, if system admins want extra fields, just add them for them and use south to migrate. I don't like generic key/value database schemas, the whole point of a powerful framework like Django is that you can easily write and rewrite custom schemas without resorting to generic approaches.
If you must allow site users/administrators to directly define their data, I'm sure others will show you how to do the first two approaches above. The third approach is what you were asking for, and a bit more crazy, I'll show you how to do. I don't recommend using it in almost all cases, but sometimes it's appropriate.
Dynamic models
Once you know what to do, this is relatively straightforward. You'll need:
1 or 2 models to store the names and types of the fields
(optional) An abstract model to define common functionality for your (subclassed) dynamic models
A function to build (or rebuild) the dynamic model when needed
Code to build or update the database tables when fields are added/removed/renamed
1. Storing the model definition
This is up to you. I imagine you'll have a model CustomCarModel and CustomField to let the user/admin define and store the names and types of the fields you want. You don't have to mirror Django fields directly, you can make your own types that the user may understand better.
Use a forms.ModelForm with inline formsets to let the user build their custom class.
2. Abstract model
Again, this is straightforward, just create a base model with the common fields/methods for all your dynamic models. Make this model abstract.
3. Build a dynamic model
Define a function that takes the required information (maybe an instance of your class from #1) and produces a model class. This is a basic example:
from django.db.models.loading import cache
from django.db import models
def get_custom_car_model(car_model_definition):
""" Create a custom (dynamic) model class based on the given definition.
"""
# What's the name of your app?
_app_label = 'myapp'
# you need to come up with a unique table name
_db_table = 'dynamic_car_%d' % car_model_definition.pk
# you need to come up with a unique model name (used in model caching)
_model_name = "DynamicCar%d" % car_model_definition.pk
# Remove any exist model definition from Django's cache
try:
del cache.app_models[_app_label][_model_name.lower()]
except KeyError:
pass
# We'll build the class attributes here
attrs = {}
# Store a link to the definition for convenience
attrs['car_model_definition'] = car_model_definition
# Create the relevant meta information
class Meta:
app_label = _app_label
db_table = _db_table
managed = False
verbose_name = 'Dynamic Car %s' % car_model_definition
verbose_name_plural = 'Dynamic Cars for %s' % car_model_definition
ordering = ('my_field',)
attrs['__module__'] = 'path.to.your.apps.module'
attrs['Meta'] = Meta
# All of that was just getting the class ready, here is the magic
# Build your model by adding django database Field subclasses to the attrs dict
# What this looks like depends on how you store the users's definitions
# For now, I'll just make them all CharFields
for field in car_model_definition.fields.all():
attrs[field.name] = models.CharField(max_length=50, db_index=True)
# Create the new model class
model_class = type(_model_name, (CustomCarModelBase,), attrs)
return model_class
4. Code to update the database tables
The code above will generate a dynamic model for you, but won't create the database tables. I recommend using South for table manipulation. Here are a couple of functions, which you can connect to pre/post-save signals:
import logging
from south.db import db
from django.db import connection
def create_db_table(model_class):
""" Takes a Django model class and create a database table, if necessary.
"""
table_name = model_class._meta.db_table
if (connection.introspection.table_name_converter(table_name)
not in connection.introspection.table_names()):
fields = [(f.name, f) for f in model_class._meta.fields]
db.create_table(table_name, fields)
logging.debug("Creating table '%s'" % table_name)
def add_necessary_db_columns(model_class):
""" Creates new table or relevant columns as necessary based on the model_class.
No columns or data are renamed or removed.
XXX: May need tweaking if db_column != field.name
"""
# Create table if missing
create_db_table(model_class)
# Add field columns if missing
table_name = model_class._meta.db_table
fields = [(f.column, f) for f in model_class._meta.fields]
db_column_names = [row[0] for row in connection.introspection.get_table_description(connection.cursor(), table_name)]
for column_name, field in fields:
if column_name not in db_column_names:
logging.debug("Adding field '%s' to table '%s'" % (column_name, table_name))
db.add_column(table_name, column_name, field)
And there you have it! You can call get_custom_car_model() to deliver a django model, which you can use to do normal django queries:
CarModel = get_custom_car_model(my_definition)
CarModel.objects.all()
Problems
Your models are hidden from Django until the code creating them is run. You can however run get_custom_car_model for every instance of your definitions in the class_prepared signal for your definition model.
ForeignKeys/ManyToManyFields may not work (I haven't tried)
You will want to use Django's model cache so you don't have to run queries and create the model every time you want to use this. I've left this out above for simplicity
You can get your dynamic models into the admin, but you'll need to dynamically create the admin class as well, and register/reregister/unregister appropriately using signals.
Overview
If you're fine with the added complication and problems, enjoy! One it's running, it works exactly as expected thanks to Django and Python's flexibility. You can feed your model into Django's ModelForm to let the user edit their instances, and perform queries using the database's fields directly. If there is anything you don't understand in the above, you're probably best off not taking this approach (I've intentionally not explained what some of the concepts are for beginners). Keep it Simple!
I really don't think many people need this, but I have used it myself, where we had lots of data in the tables and really, really needed to let the users customise the columns, which changed rarely.
Database
Consider your database design once more.
You should think in terms of how those objects that you want to represent relate to each other in the real world and then try to generalize those relations as much as you can, (so instead of saying each truck has a permit, you say each vehicle has an attribute which can be either a permit, load amount or whatever).
So lets try it:
If you say you have a vehicle and each vehicle can have many user specified attributes consider the following models:
class Attribute(models.Model):
type = models.CharField()
value = models.CharField()
class Vehicle(models.Model):
attribute = models.ManyToMany(Attribute)
As noted before, this is a general idea which enables you to add as much attributes to each vehicle as you want.
If you want specific set of attributes to be available to the user you can use choices in the Attribute.type field.
ATTRIBUTE_CHOICES = (
(1, 'Permit'),
(2, 'Manufacturer'),
)
class Attribute(models.Model):
type = models.CharField(max_length=1, choices=ATTRIBUTE_CHOICES)
value = models.CharField()
Now, perhaps you would want each vehicle sort to have it's own set of available attributes. This can be done by adding yet another model and set foreign key relations from both Vehicle and Attribute models to it.
class VehicleType(models.Model):
name = models.CharField()
class Attribute(models.Model):
vehicle_type = models.ForeigngKey(VehicleType)
type = models.CharField()
value = models.CharField()
class Vehicle(models.Model):
vehicle_type = models.ForeigngKey(VehicleType)
attribute = models.ManyToMany(Attribute)
This way you have a clear picture of how each attribute relates to some vehicle.
Forms
Basically, with this database design, you would require two forms for adding objects into the database. Specifically a model form for a vehicle and a model formset for attributes. You could use jQuery to dynamically add more items on the Attribute formset.
Note
You could also separate Attribute class to AttributeType and AttributeValue so you don't have redundant attribute types stored in your database or if you want to limit the attribute choices for the user but keep the ability to add more types with Django admin site.
To be totally cool, you could use autocomplete on your form to suggest existing attribute types to the user.
Hint: learn more about database normalization.
Other solutions
As suggested in the previous answer by Stuart Marsh
On the other hand you could hard code your models for each vehicle type so that each vehicle type is represented by the subclass of the base vehicle and each subclass can have its own specific attributes but that solutions is not very flexible (if you require flexibility).
You could also keep JSON representation of additional object attributes in one database field but I am not sure this would be helpfull when querying attributes.
Here is my simple test in django shell- I just typed in and it seems work fine-
In [25]: attributes = {
"__module__": "lekhoni.models",
"name": models.CharField(max_length=100),
"address": models.CharField(max_length=100),
}
In [26]: Person = type('Person', (models.Model,), attributes)
In [27]: Person
Out[27]: class 'lekhoni.models.Person'
In [28]: p1= Person()
In [29]: p1.name= 'manir'
In [30]: p1.save()
In [31]: Person.objects.a
Person.objects.aggregate Person.objects.all Person.objects.annotate
In [32]: Person.objects.all()
Out[33]: [Person: Person object]
It seems very simple- not sure why it should not be a considered an option- Reflection is very common is other languages like C# or Java- Anyway I am very new to django things-
Are you talking about in a front end interface, or in the Django admin?
You can't create real fields on the fly like that without a lot of work under the hood. Each model and field in Django has an associated table and column in the database. To add new fields usually requires either raw sql, or migrations using South.
From a front end interface, you could create pseudo fields, and store them in a json format in a single model field.
For example, create an other_data text field in the model. Then allow users to create fields, and store them like {'userfield':'userdata','mileage':54}
But I think if you're using a finite class like vehicles, you would create a base model with the basic vehicle characteristics, and then create models that inherits from the base model for each of the vehicle types.
class base_vehicle(models.Model):
color = models.CharField()
owner_name = models.CharField()
cost = models.DecimalField()
class car(base_vehicle):
mileage = models.IntegerField(default=0)
etc