I'm defining a ChoiceField based on a model's datas.
field = forms.ChoiceField(choices=[[r.id, r.name] for r in Model.objects.all()])
However I'd like to prepend my options with an empty one to select "no" objects.
But I can't find a nice way to prepend that.
All my tests like :
field = forms.ChoiceField(choices=[[0, '----------']].extend([[r.id, r.name] for r in Model.objects.all()]))
Returns me a "NoneType object not iterable" error.
The only way I've found until now is the following :
def append_empty(choices):
ret = [[0, '----------']]
for c in choices:
ret.append(c)
return ret
And when I define my field :
forms.ChoiceField(choices=append_empty([[r.id, r.name] for r in
Restaurant.objects.all()]), required=False)
However I'd like to keep my code clean and not have that kind of horrors.
Would you have an idea for me ? :p
Thanks by advance.
An easy answer is to do:
field = forms.ChoiceField(choices=[[0, '----------']] + [[r.id, r.name] for r in Model.objects.all()])
Unfortunately, your approach is flawed. Even with your 'working' approach, the field choices are defined when the form is defined, not when it is instantiated - so if you add elements to the Model table, they will not appear in the choices list.
You can avoid this by doing the allocation in the __init__ method of your Form.
However, there is a much easier approach. Rather than messing about with field choices dynamically, you should use the field that is specifically designed to provide choices from a model - ModelChoiceField. Not only does this get the list of model elements dynamically at instantiation, it already includes a blank choice by default. See the documentation.
Since this question and its answer almost solved a problem I just had I'd like to add something. For me, the id had to be empty because the model didn't recognise '0' as a valid option, but it accepted empty (null=True, blank=True). In the initializer:
self.fields['option_field'].choices = [
('', '------')] + [[r.id, r.name] for r in Model.objects.all()]
Related
I haven't had much luck finding other questions that helped with this, but apologies if I missed something and this is a duplicate.
I'm trying to add to some ManyToMany fields, without having to explicitly type out the names of the fields in the code (because the function I'm working on will be used to add to multiple fields and I'd rather not have to repeat the same code for every field). I'm having a hard time using ._meta to reference the model and field objects correctly so that .add() doesn't throw an "AttributeError: 'ManyToManyField' object has no attribute 'add'".
This is simplified because the full body of code is too long to post it all here, but in models.py, I have models defined similar to this:
class Sandwich(models.Model):
name = models.CharField(max_length=MAX_CHAR_FIELD)
veggies = models.ManyToManyField(Veggie)
meats = models.ManyToManyField(Meat)
class Veggie(models.Model):
name = models.CharField(max_length=MAX_CHAR_FIELD)
class Meat(models.Model):
name = models.CharField(max_length=MAX_CHAR_FIELD)
Once instances of these are created and saved, I can successfully use .add() like this:
blt = Sandwich(name='blt')
blt.save()
lettuce = Veggies(name='lettuce')
lettuce.save()
tomato = Veggies(name='tomato')
tomato.save()
bacon = Meat(name='bacon')
bacon.save()
blt.veggies.add(lettuce)
blt.veggies.add(tomato)
blt.meats.add(bacon)
But if I try to use ._meta to get blt's fields and add to them that way, I can't. ie something like this,
field_name='meats'
field = blt._meta.get_field(field_name)
field.add(bacon)
will throw "AttributeError: 'ManyToManyField' object has no attribute 'add'".
So, how can I use ._meta or a similar approach to get and refer to these fields in a way that will let me use .add()? (bonus round, how and why is "blt.meats" different than "blt._meta.get_field('meats')" anyway?)
Why do you want to do
field = blt._meta.get_field(field_name)
field.add(bacon)
instead of
blt.meats.add(bacon)
in the first place?
If what you want is to access the attribute meats on the blt instance of the Sandwich class because you have the string 'meats' somewhere, then it's plain python you're after:
field_string = 'meats'
meats_attribute = getattr(blt, field_string, None)
if meats_attribute is not None:
meats_attribute.add(bacon)
But if your at the point where you're doing that sort of thing you might want to revise your data modelling.
Bonus round:
Call type() on blt.meats and on blt._meta.get_field(field_name) and see what each returns.
One is a ManyToManyField, the other a RelatedManager. First is an abstraction that allows you to tell Django you have a M2M relation between 2 models, so it can create a through table for you, the other is an interface for you to query those related objects (you can call .filter(), .exclude() on it... like querysets): https://docs.djangoproject.com/en/4.1/ref/models/relations/#django.db.models.fields.related.RelatedManager
Codenerix
Has anyone knows how to use correctly ng-readonly in a GenModelForm when coming from a sublist tab (GenList) who calls a GenCreateModal windows?
Structure is a master-detail, sublist tab has pk of master table and calls GenCreateModal with this pk argument of master table.
GenCreateModal receives pk argument in his asociated form (the mentioned GenModelForm) and can use it. The goal is to disable field with ng-disabled if pk argument of master table is filled. This way when create from another list of detail table without arguments, field can be filled with a value selecting it with the dropdown, and when coming from master table it cannot be modified and it will be assigned to master pk value.
I tried to do it that way:
First assign 'client' on GenCreateModal with:
def get_initial(self):
client = self.kwargs.get('pk', None)
if client:
self.kwargs['client'] = client
return self.kwargs
Then read it on the GenModelform with:
def __init__(self, *args, **kwargs):
super(DetailForm, self).__init__(*args, **kwargs)
if kwargs.get('initial', None) and kwargs['initial'].get('client', None):
self.fields['client'].widget.attrs[u'ng-readonly'] = 'true'
But it do not work with dropdown fields. Field can be modified.
Cause is that in templatetags_list.py of codenerix we have:
def inireadonly(attrs, i):
field = ngmodel(i)
return addattr(attrs, 'ng-readonly=readonly_{0}'.format(field))
This code set ng-readonly to "true readonly_client" instead of "true" when it comes with value "true" from GenModelForm, values are concatenated.
I found a workaround with:
self.fields['client'].widget.attrs[u'ng-readonly'] = 'true || '
this way the end value will be "true || readonly_client" that result on "true" as desired when evaluated, but I think it is not the proper way.
On my personal fork of django-codenerix I have changed the function to (functions is on two py files, should change both):
def inireadonly(attrs, i):
field = ngmodel(i)
if attrs.get('ng-readonly', None) is None:
attrs = addattr(attrs, 'ng-readonly=readonly_{0}'.format(field))
return attrs
This way it respects the value when it comes filled form GenModelForm, but I'm not sure about inconveniences and collateral effects. For example when want to concatenate conditions, with that change should read old value, concatenate manually and set new value. I think it should be a better way to do it and 'ng-readonly=readonly_{0}'.format(field) should have a functionality that I haven't discovered yet. Don't want to lose it when I discover it. So I revert the change and look for another solution.
Currently I'm using
self.fields['client'].widget.attrs[u'ng-disabled'] = 'true'
and it goes OK, I'm using this way and I have no problem now, but I'm curious about the way to use ng-readonly if I need it on the future. That's because with ng-readonly we can select text on fields with the mouse for example and can not select it with ng-disabled. In some cases it could be of interest.
Has anyone knows how to use ng-readonly in a correct way?
Has anyone knows the functionality of 'ng-readonly=readonly_{0}'.format(field)?
You can define an extra attribute to your fields in your forms. Add {'extra': ['ng-disabled=true']} in the field of your GenModelForm, inside your __groups__ method. Example:
def __groups__(self):
g = [
(_('Info'), 12,
['client', 6, {'extra': ['ng-disabled=true']}],
)
]
return g
You should use ng-disabled as you are doing. This is the way we do it in Django Codenerix Example # Gibhub (lines 41 and 42) and this is how it has been developed for StaticSelects (line 228) as well.
I commonly find myself writing the same criteria in my Django application(s) more than once. I'll usually encapsulate it in a function that returns a Django Q() object, so that I can maintain the criteria in just one place.
I will do something like this in my code:
def CurrentAgentAgreementCriteria(useraccountid):
'''Returns Q that finds agent agreements that gives the useraccountid account current delegated permissions.'''
AgentAccountMatch = Q(agent__account__id=useraccountid)
StartBeforeNow = Q(start__lte=timezone.now())
EndAfterNow = Q(end__gte=timezone.now())
NoEnd = Q(end=None)
# Now put the criteria together
AgentAgreementCriteria = AgentAccountMatch & StartBeforeNow & (NoEnd | EndAfterNow)
return AgentAgreementCriteria
This makes it so that I don't have to think through the DB model more than once, and I can combine the return values from these functions to build more complex criterion. That works well so far, and has saved me time already when the DB model changes.
Something I have realized as I start to combine the criterion from these functions that is that a Q() object is inherently tied to the type of object .filter() is being called on. That is what I would expect.
I occasionally find myself wanting to use a Q() object from one of my functions to construct another Q object that is designed to filter a different, but related, model's instances.
Let's use a simple/contrived example to show what I mean. (It's simple enough that normally this would not be worth the overhead, but remember that I'm using a simple example here to illustrate what is more complicated in my app.)
Say I have a function that returns a Q() object that finds all Django users, whose username starts with an 'a':
def UsernameStartsWithAaccount():
return Q(username__startswith='a')
Say that I have a related model that is a user profile with settings including whether they want emails from us:
class UserProfile(models.Model):
account = models.OneToOneField(User, unique=True, related_name='azendalesappprofile')
emailMe = models.BooleanField(default=False)
Say I want to find all UserProfiles which have a username starting with 'a' AND want use to send them some email newsletter. I can easily write a Q() object for the latter:
wantsEmails = Q(emailMe=True)
but find myself wanting to something to do something like this for the former:
startsWithA = Q(account=UsernameStartsWithAaccount())
# And then
UserProfile.objects.filter(startsWithA & wantsEmails)
Unfortunately, that doesn't work (it generates invalid PSQL syntax when I tried it).
To put it another way, I'm looking for a syntax along the lines of Q(account=Q(id=9)) that would return the same results as Q(account__id=9).
So, a few questions arise from this:
Is there a syntax with Django Q() objects that allows you to add "context" to them to allow them to cross relational boundaries from the model you are running .filter() on?
If not, is this logically possible? (Since I can write Q(account__id=9) when I want to do something like Q(account=Q(id=9)) it seems like it would).
Maybe someone suggests something better, but I ended up passing the context manually to such functions. I don't think there is an easy solution, as you might need to call a whole chain of related tables to get to your field, like table1__table2__table3__profile__user__username, how would you guess that? User table could be linked to table2 too, but you don't need it in this case, so I think you can't avoid setting the path manually.
Also you can pass a dictionary to Q() and a list or a dictionary to filter() functions which is much easier to work with than using keyword parameters and applying &.
def UsernameStartsWithAaccount(context=''):
field = 'username__startswith'
if context:
field = context + '__' + field
return Q(**{field: 'a'})
Then if you simply need to AND your conditions you can combine them into a list and pass to filter:
UserProfile.objects.filter(*[startsWithA, wantsEmails])
Suppose I have three django models:
class Section(models.Model):
name = models.CharField()
class Size(models.Model):
section = models.ForeignKey(Section)
size = models.IntegerField()
class Obj(models.Model):
name = models.CharField()
sizes = models.ManyToManyField(Size)
I would like to import a large amount of Obj data where many of the sizes fields will be identical. However, since Obj has a ManyToMany field, I can't just test for existence like I normally would. I would like to be able to do something like this:
try:
x = Obj(name='foo')
x.sizes.add(sizemodel1) # these can be looked up with get_or_create
...
x.sizes.add(sizemodelN) # these can be looked up with get_or_create
# Now test whether x already exists, so I don't add a duplicate
try:
Obj.objects.get(x)
except Obj.DoesNotExist:
x.save()
However, I'm not aware of a way to get an object this way, you have to just pass in keyword parameters, which don't work for ManyToManyFields.
Is there any good way I can do this? The only idea I've had is to build up a set of Q objects to pass to get:
myq = myq & Q(sizes__id=sizemodelN.id)
But I am not sure this will even work...
Use a through model and then .get() against that.
http://docs.djangoproject.com/en/dev/topics/db/models/#extra-fields-on-many-to-many-relationships
Once you have a through model, you can .get() or .filter() or .exists() to determine the existence of an object that you might otherwise want to create. Note that .get() is really intended for columns where unique is enforced by the DB - you might have better performance with .exists() for your purposes.
If this is too radical or inconvenient a solution, you can also just grab the ManyRelatedManager and iterate through to determine if the object exists:
object_sizes = obj.sizes.all()
exists = object_sizes.filter(id__in = some_bunch_of_size_object_ids_you_are_curious_about).exists()
if not exists:
(your creation code here)
Your example doesn't make much sense because you can't add m2m relationships before an x is saved, but it illustrated what you are trying to do pretty well. You have a list of Size objects created via get_or_create(), and want to create an Obj if no duplicate obj-size relationship exists?
Unfortunately, this is not possible very easily. Chaining Q(id=F) & Q(id=O) & Q(id=O) doesn't work for m2m.
You could certainly use Obj.objects.filter(size__in=Sizes) but that means you'd get a match for an Obj with 1 size in a huge list of sizes.
Check out this post for an __in exact question, answered by Malcolm, so I trust it quite a bit.
I wrote some python for fun that could take care of this.
This is a one time import right?
def has_exact_m2m_match(match_list):
"""
Get exact Obj m2m match
"""
if isinstance(match_list, QuerySet):
match_list = [x.id for x in match_list]
results = {}
match = set(match_list)
for obj, size in \
Obj.sizes.through.objects.filter(size__in=match).values_list('obj', 'size'):
# note: we are accessing the auto generated through model for the sizes m2m
try:
results[obj].append(size)
except KeyError:
results[obj] = [size]
return bool(filter(lambda x: set(x) == match, results.values()))
# filter any specific objects that have the exact same size IDs
# if there is a match, it means an Obj exists with exactly
# the sizes you provided to the function, no more.
sizes = [size1, size2, size3, sizeN...]
if has_exact_m2m_match(sizes):
x = Obj.objects.create(name=foo) # saves so you can use x.sizes.add
x.sizes.add(sizes)
What is the correct method for validating input for a custom multiwidget in each of these cases:
if I want to implement a custom Field?
if I want to use an existing database field type (say DateField)?
The motivation for this comes from the following two questions:
How do I use django's multi-widget?
Django subclassing multiwidget
I am specifically interested in the fact that I feel I have cheated. I have used value_from_datadict() like so:
def value_from_datadict(self, data, files, name):
datelist = [widget.value_from_datadict(data, files, name + '_%s' % i) for i, widget in enumerate(self.widgets)]
try:
D = date(day=int(datelist[0]), month=int(datelist[1]), year=int(datelist[2]))
return str(D)
except ValueError:
return None
Which looks through the POST dictionary and constructs a value for my widget (see linked questions). However, at the same time I've tacked on some validation; namely if the creation of D as a date object fails, I'm returning None which will fail in the is_valid() check.
My third question therefore is should I be doing this some other way? For this case, I do not want a custom field.
Thanks.
You validate your form fields just like any other fields, implementing the clean_fieldname method in your form. If your validation logic spreads across many form fields (which is nto the same as many widgets!) you put it in your form's clean() method.
http://docs.djangoproject.com/en/1.2/ref/forms/validation/
According to the documentation, validation is the responsibility of the field behind the widget, not the widget itself. Widgets should do nothing but present the input for the user and pass input data back to the field.
So, if you want to validate data that's been submitted, you should write a validator.
This is especially important with MultiWidgets, as you can have more than one aspect of the data error out. Each aspect needs to be returned to the user for consideration, and the built in way to do that is to write validators and place them in the validators attribute of the field.
Contrary to the documentation, you don't have to do this per form. You can, instead, extend one of the built in forms and add an entry to default_validators.
One more note: If you're going to implement a MultiWidget, your form is going to pass some sort of 'compressed' data back to it to render. The docs say:
This method takes a single “compressed” value from the field and returns a list of “decompressed” values. The input value can be assumed valid, but not necessarily non-empty.
-Widgets
Just make sure you're handling that output correctly and you'll be fine.