I am using a third party application and i wish to override the save() method of the original model to validate some data.
class CustomState(State):
class Meta:
proxy = True
def save(self, *args, **kwargs):
print('hellooo in save method of state')
super(State, self).save(*args, **kwargs)
However the code snippet above does not run.
Therefore my question is is there a way to override the save method of a model ? Or if thats not possible , is there a way to add in validation before the third party model instance is created?
the issue has nothing to do with the fact that your Model is proxy but the wrong way how you call the parent super().save():
class CustomState(State):
class Meta:
proxy = True
def save(self, *args, **kwargs):
print('hellooo in save method of state')
# The wrong way to call super
# super(State, self).save(*args, **kwargs)
super(CustomState, self).save(*args, **kwargs)
have a look at this tutorial, topic A super() Deep Dive
Related
The goal is removing of duplicates from list field while saving model. For example creation in migration:
def migrate_model(apps, *args):
MyModel = apps.get_model('my_app.MyModel')
m = MyModel.objects.create(
array_field=['123','123'],
)
m.array_field # ['123']
I tried to overwrite save but it doesn't work
class MyModel(models.Model):
array_field = ArrayField(models.CharField(max_length=5))
def save(self, *args, **kwargs):
if self.array_field:
self.array_field = list(set(self.array_field))
super(MyModel, self).save(*args, **kwargs)
How can I do this?
Careful, the save() method is NOT called when using create() according to django docs.
Maybe that is causing you the problems, because your overriden save method doesn't actually gets called.
I have my serializers code set up as follows:
class ProductSerializer(serializers.ModelSerializer):
"""
* Serializes Products.
"""
def __init__(self, *args, **kwargs):
print kwargs.pop('product_passed')
super(ProductSerializer, self).__init__(*args, **kwargs)
Now, this serializer is being called from a view using the code below:
product_passed = Product.objects.get(pk=pk)
product_serializer = ProductSerializer(product_passed)
What I want to do is call the product_passed from my serializer init method. How can I do this? Right now, my method does not work.
Pass it like this:
product_serializer = ProductSerializer(product_passed, product_passed= product_passed)
And access it from kwargs: kwargs.get('product_passed')
I'm trying to perform some custom validation on a model and I'm getting confused. Let me be specific. Let's say my code is as follows:
class FooManager(models.Manager):
def create_foo(self, name):
return self.create(foo_name = name)
class Foo(models.Model):
foo_name = models.CharField(max_length=30)
objects = FooManager()
def clean(self):
...
def save(self, *args, **kwargs):
self.full_clean()
super(User, self).save(*args, **kwargs)
Now, when I am working with this model from the shell, if I call:
f = Foo.objects.create_foo("")
It will raise a validation error before I get a chance to call save() on f. Why does this happen? Shouldn't the validation error only be raised once I call f.save()?
Note: the same thing happens if I use objects.create() as opposed to the custom defined create method. Any help would be greatly appreciated, as I'm finding validations in django to be fairly frustrating.
create() will automatically save, so even if you fix your error - you will still have to make sure the arguments to create fulfill the database requirements to save a record.
You forgot to put self in your manager
class FooManager(models.Manager):
def create_foo(self, name):
return self.create(foo_name = name)
I am trying to add dynamically new form fields (I used this blog post), for a form used in admin interface :
class ServiceRoleAssignmentForm(forms.ModelForm):
class Meta:
model = ServiceRoleAssignment
def __init__(self, *args, **kwargs):
super(ServiceRoleAssignmentForm, self).__init__(*args, **kwargs)
self.fields['test'] = forms.CharField(label='test')
class ServiceRoleAssignmentAdmin(admin.ModelAdmin):
form = ServiceRoleAssignmentForm
admin.site.register(ServiceRoleAssignment, ServiceRoleAssignmentAdmin)
However, no matter what I try, the field doesn't appear on my admin form ! Could it be a problem related to the way admin works ? Or to ModelForm ?
Thank for any help !
Sébastien
PS : I am using django 1.3
When rendering your form in template, fields enumerating from fieldsets variable, not from fields. Sure you can redefine fieldsets in your AdminForm, but then validations will fail as original form class doesn't have such field. One workaround I can propose is to define this field in form definition statically and then redefine that field in form's init method dynamically. Here is an example:
class ServiceRoleAssignmentForm(forms.ModelForm):
test = forms.Field()
class Meta:
model = ServiceRoleAssignment
def __init__(self, *args, **kwargs):
super(ServiceRoleAssignmentForm, self).__init__(*args, **kwargs)
# Here we will redefine our test field.
self.fields['test'] = forms.CharField(label='test2')
I actually have a the same issue which I'm working through at the moment.
While not ideal, I have found a temporary workaround that works for my use case. It might be of use to you?
In my case I have a static name for the field, so I just declared it in my ModelForm. as normal, I then override the init() as normal to override some options.
ie:
def statemachine_form(for_model=None):
"""
Factory function to create a special case form
"""
class _StateMachineBaseModelForm(forms.ModelForm):
_sm_action = forms.ChoiceField(choices=[], label="Take Action")
class Meta:
model = for_model
def __init__(self, *args, **kwargs):
super(_StateMachineBaseModelForm, self).__init__(*args, **kwargs)
actions = (('', '-----------'),)
for action in self.instance.sm_state_actions():
actions += ((action, action),)
self.fields['_sm_action'] = forms.ChoiceField(choices=actions,
label="Take Action")
if for_model: return _StateMachineBaseModelForm
class ContentItemAdmin(admin.ModelAdmin):
form = statemachine_form(for_model=ContentItem)
Now as I mentioned before, this is not entirely 'dynamic', but this will do for me for the time being.
I have the exact same problem that, if I add the field dynamically, without declaring it first, then it doesn't actually exist. I think this does in fact have something to do with the way that ModelForm creates the fields.
I'm hoping someone else can give us some more info.
Django - Overriding get_form to customize admin forms based on request
Try to add the field before calling the super.init:
def __init__(self, *args, **kwargs):
self.fields['test'] = forms.CharField(label='test')
super(ServiceRoleAssignmentForm, self).__init__(*args, **kwargs)
say I've got:
class LogModel(models.Model):
message = models.CharField(max_length=512)
class Assignment(models.Model):
someperson = models.ForeignKey(SomeOtherModel)
def save(self, *args, **kwargs):
super(Assignment, self).save()
old_person = #?????
LogModel(message="%s is no longer assigned to %s"%(old_person, self).save()
LogModel(message="%s is now assigned to %s"%(self.someperson, self).save()
My goal is to save to LogModel some messages about who Assignment was assigned to. Notice that I need to know the old, presave value of this field.
I have seen code that suggests, before super().save(), retrieve the instance from the database via primary key and grab the old value from there. This could work, but is a bit messy.
In addition, I plan to eventually split this code out of the .save() method via signals - namely pre_save() and post_save(). Trying to use the above logic (Retrieve from the db in pre_save, make the log entry in post_save) seemingly fails here, as pre_save and post_save are two seperate methods. Perhaps in pre_save I can retrieve the old value and stick it on the model as an attribute?
I was wondering if there was a common idiom for this. Thanks.
A couple of months ago I found somewhere online a good way to do this...
class YourModel(models.Model):
def __init__(self, *args, **kwargs):
super(YourModel, self).__init__(*args, **kwargs)
self.original = {}
id = getattr(self, 'id', None)
for field in self._meta.fields:
if id:
self.original[field.name] = getattr(self, field.name, None)
else:
self.original[field.name] = None
Basically a copy of the model fields will get saved to self.original. You can then access it elsewhere in the model...
def save(self, *args, **kwargs):
if self.original['my_property'] != self.my_property:
# ...
It can be easily done with signals. There are, respectively a pre-save and post-save signal for every Django Model.
So I came up with this:
class LogModel(models.Model):
message = models.CharField(max_length=512)
class Assignment(models.Model):
someperson = models.ForeignKey(SomeOtherModel)
import weakref
_save_magic = weakref.WeakKeyDictionary()
#connect(pre_save, Assignment)
def Assignment_presave(sender, instance, **kwargs):
if instance.pk:
_save_magic[instance] = Assignment.objects.get(pk=instance.pk).someperson
#connect(post_save, Assignment)
def Assignment_postsave(sender, instance, **kwargs):
old = None
if instance in _save_magic:
old = _save_magic[instance]
del _save_magic[instance]
LogModel(message="%s is no longer assigned to %s"%(old, self).save()
LogModel(message="%s is now assigned to %s"%(instance.someperson, self).save()
What does StackOverflow think? Anything better? Any tips?