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How to run a model's function with DTL?

I am fairly new to django and I am trying the following:
I am making an ordering web app for a nearby business. I am trying to add all the calories in a combo.
I have a model "Consumable", this represent the different food and drinks there are.
Here is the code for the "Consumable" Model:
class Consumable(models.Model):
name = models.CharField(max_length=80, unique=True)
category = models.ForeignKey(FoodCategory, null=True, on_delete=models.SET_NULL)
price= models.FloatField(default=0.00)
calories = models.IntegerField(blank=False)
image = models.ImageField(upload_to="images/Food/")
description = RichTextField(blank=True, max_length=500)
restaurant = models.ForeignKey(Place, on_delete=models.CASCADE)
added = models.DateTimeField(auto_now_add=True)
updated = models.DateTimeField(auto_now=True)
def __str__(self):
return self.name
Then, I have a model called "Meal" which has the following code:
class Meal(models.Model):
name = models.CharField(max_length=100)
image = models.ImageField(upload_to='images/photos/meals')
consumables = models.ManyToManyField(Consumable, related_name="consumable")
restaurant = models.ForeignKey(Place, on_delete=models.CASCADE)
price = models.FloatField()
def add_cals(meal_consumables):
total_calories = 0
for x in meal_consumables.values():
global total_calories += float(x.calories)
return total_calories
I am trying to call this model's function, add_cals from my HTML file using the DTL (Django Template Language).
For example, if you have a model stored with the variable x in your view, and it is in the view's context dictionary, you could simply call the model by using <p>{{x}}</p>, for example. And if the model has a variable x1, you could call it as <p>{{x.x1}}</p> and it works fine. However, if the x model from my example has a function
add_x(x):
return x
then it wouldn't work when you call it as <p>{{x.add_x(1)}}</p> for some reason. Could some wise individual out there in this world be so humble to share his or her knowledge with me in order to help me?
Thanks to everyone who tries.

Django Model Occurrence Count

I'm fairly new to Django and I'm in need of assistance with my models.
class Region(models.Model):
region_name = models.CharField(max_length=10)
def __str__(self):
return self.region_name
class Property(models.Model):
prop_name = models.CharField(max_length=200)
region_name = models.ForeignKey(Region, on_delete=models.CASCADE, verbose_name="Region")
prop_code = models.IntegerField(default=0, verbose_name="Property")
def __str__(self):
return self.prop_name
class Sale(models.Model):
prop_name = models.ForeignKey(Property, on_delete=models.CASCADE)
employee = models.ForeignKey(User, on_delete=models.CASCADE, verbose_name="Person")
prop_state = models.CharField(null=True, max_length=5, choices=[('new','New'),('used','Used')])
date = models.DateField('Sale Date')
def __str__(self):
return '%s : %s %s - %s' % (self.prop_name.prop_name, self.employee, self.date, self.prop_state)
Here are my models. Property inherits from Region and Sale inherits from property. What I want to do is count the number of sales in a region and the number of sales on a specific property. However I do not know which would be the best way to approach this. I've tried using a lambda as a model field that uses the count() function but I wasn't able to see much success with that. Please let me know if you have any suggestions.

If you already have your Property/Region objects, something like this should work
sales_per_property = Sale.objects.filter(prop_name=property).count()
sales_per_region = Sale.objects.filter(prop_name__region_name=region).count()
Edit:
Seeing that you tried to add a lambda function to the model field, this may be more what you are looking for.
class Region(models.Model):
...
#property
def sales(self):
return Sale.objects.filter(prop_name__region_name=self).count()
and similarly for Property. Simply access the property using region.sales

You can annotate your querysets for Region and Property. For example:
from django.db.models import Count
regions = Region.objects.annotate(sales=Count('property__sale'))
properties = Property.objects.annotate(sales=Count('sale'))
The Regions/Propertys that arise from these querysets will have an extra attribute .sales that contains the number of related Sale objects.

Did I set this up correctly?

I'm asking if I set up the create method up correctly. Or does it need to be added for the other two models as well? How would this be changed?
class PointModel(models.Model):
x = models.IntegerField()
y = models.IntegerField()
index = models.IntegerField()
class DatetimeRangeModel(models.Model):
start_datetime = models.CharField(max_length=14)
end_datetime = models.CharField(max_length=14)
class PlanModel(models.Model):
data_number = models.IntegerField()
data_datetime_range = models.ForeignKey(DatetimeRangeModel, blank=True, null=True, on_delete=models.SET_NULL)
data_polygon = models.ForeignKey(PointModel, blank=True, null=True, on_delete=models.SET_NULL)
#classmethod
def create(cls, data_number, data_datetime_range, data_polygon):
plan = cls(data_number=data_number, data_datetime_range = data_datetime_range,
data_polygon=data_polygon)
return plan
EDIT: I change the structure which fixed the undefined and added some logic that prevents the PlanModel from being deleted with the "blank=True, null=True, on_delete=models.SET_NULL"
Does this look right?

see the docs for creating objects
#classmethod
def create(cls, title):
book = cls(title=title)
# do something with the book
return book
there's no much reason to add those unless you have something to add there on the # do something with the book line
EDIT: instead of calling create you're usually do:
plan = PlanModel(data_number=1, ....)
plan.save()
or sometimes:
plan = PlanModel()
plan.data_number=1
...
plan.save()

How to store functions in django models

edit: I completely rewrote the question as the original one didn't clearly explain my question
I want to run a function which is specific to each particular model instance.
Ideally I want something like this:
class MyModel(models.Model):
data = models.CharField(max_length=100)
perform_unique_action = models.FunctionField() #stores a function specific to this instance
x = MyModel(data='originalx', perform_unique_action=func_for_x)
x.perform_unique_action() #will do whatever is specified for instance x
y = MyModel(data='originaly', perform_unique_action=func_for_y)
y.perform_unique_action() #will do whatever is specified for instance y
However there is no datatype FunctionField. Normally this would be solvable with inheritance, and creating subclasses of MyModel, maybe like this:
class MyModel(models.Model):
data = models.CharField(max_length=100)
perform_unique_action = default_function
class MyModelX(MyModel):
perform_unique_action = function_X
class MyModelY(MyModel):
perform_unique_action = function_Y
x = MyModelX(data='originalx')
x.perform_unique_action() #will do whatever is specified for instance x
y = MyModelY(data='originaly')
y.perform_unique_action() #will do whatever is specified for instance y
Unfortunately, I don't think I can use inheritance because I am trying to access the function this way:
class MyModel(models.Model):
data = models.CharField(max_length=100)
perform_unique_action = default_function
class SecondModel(models.Model):
other_data = models.IntegerField()
mymodel = models.ForeignKey(MyModel)
secondmodel = SecondModel.objects.get(other_data=3)
secondmodel.mymodel.perform_unique_action()
The problem seems to be that I don't know what type the foreign key is going to be in SecondModel if I override the perform_unique_action in subclasses.
Can I access MyModel from SecondModel as a foreign key and still have a unique function for each instance of MyModel?

This works for me. I haven't tested it, but you should be able to create another class and override their methods and it'll work. Check the class Meta line, it'll treat it as an abstract class. Here's an example of my actual classes that I'm working on right now.
EDIT: Added VoteComment class and tested it. It works as expected!
class Vote(models.Model):
VOTE_ENUM = (
(VoteEnum.DOWN_VOTE, VoteEnum.toString(VoteEnum.DOWN_VOTE)),
(VoteEnum.NONE, VoteEnum.toString(VoteEnum.NONE)),
(VoteEnum.UP_VOTE, VoteEnum.toString(VoteEnum.UP_VOTE)),
)
question = models.ForeignKey(Question, null=False, editable=False, blank=False)
voter = models.ForeignKey(User, blank=False, null=False, editable=False)
vote_type = models.SmallIntegerField(default=0, null=False, blank=False, choices=VOTE_ENUM)
class Meta:
abstract = True
def is_upvote(self):
return self.vote_type > 0
def is_downvote(self):
return self.vote_type < 0
class VoteAnswer(Vote):
answer = models.ForeignKey(Answer, null=False, editable=False, blank=False)
class Meta:
unique_together = (("voter", "answer"),) # to prevent user from voting on the same question/answer/comment again
def __unicode__(self):
vote_type = "UP" if vote_type > 0 else ("DOWN" if vote_type < 0 else "NONE")
return u"{0}: [{1}] {2}".format(user.username, vote_type, answer.text[:32])
def is_upvote(self):
return "FOO! "+str(super(VoteAnswer, self).is_upvote())
class VoteComment(Vote):
comment = models.ForeignKey(Comment, null=False, editable=False, blank=False)
class Meta:
unique_together = (("voter", "comment"),) # to prevent user from voting on the same question/answer/comment again
def __unicode__(self):
vote_type = "UP" if vote_type > 0 else ("DOWN" if vote_type < 0 else "NONE")
return u"{0}: [{1}] {2}".format(user.username, vote_type, comment.text[:32])
def is_upvote(self):
return "BAR!"

I came up with two ways of having a specific function defined for each object. One was using marshal to create bytecode which can be stored in the database (not a good way), and the other was by storing a reference to the function to be run, as suggested by Randall. Here is my solution using a stored reference:
class MyModel(models.Model):
data = models.CharField(max_length=100)
action_module = models.CharField(max_length=100)
action_function = models.CharField(max_length=100)
class SecondModel(models.Model):
other_data = models.IntegerField()
mymodel = models.ForeignKey(MyModel)
secondmodel_obj = SecondModel.objects.get(other_data=3)
#The goal is to run a function specific to the instance
#of MyModel referred to in secondmodel_obj
module_name = secondmodel_obj.mymodel.action_module
func_name = secondmodel_obj.mymodel.action_function
module = __import__(module_name)
func = vars(module)[func_name]
func()
Thanks to everyone who replied, I couldn't have got to this answer if it weren't for your help.

You could achive some similar behavior overriding the save method. And providing special callbacks to your instances.
Something like:
def default_function(instance):
#do something with the model instance
class ParentModel(model.Model):
data = models.CharField()
callback_function = default_function
def save(self, *args, **kwargs):
if hasattr(self, 'callback_function'):
self.callback_function(self)
super(ParentModel, self).save(*args, **kwargs)
class ChildModel():
different_data = models.CharField()
callback_function = other_fun_specific_to_this_model
instance = ChildModel()
#Specific function to this particular instance
instance.callback_function = lambda inst: print inst.different_data
instance.save()

You can write endpoints on your server and limit their access to just your self. Then store in each model instance corresponding url. For example:
views.py
def funx_x(request):
pass
def func_y(request):
pass
models.py:
class MyModel(models.Model):
data = models.CharField(max_length=100)
perform_unique_action = models.URLField()
and then:
x = MyModel(data='originalx', perform_unique_action='http://localhost/funx_x')
requests.post(x.perform_unique_action)

i dont know whether i understand u correct or not. but you can check out this example here.
Example:
A string representing an attribute on the model. This behaves almost the same as the callable, but self in this context is the model instance. Here's a full model example:
class Person(models.Model):
name = models.CharField(max_length=50)
birthday = models.DateField()
def decade_born_in(self):
return self.birthday.strftime('%Y')[:3] + "0's"
decade_born_in.short_description = 'Birth decade'
class PersonAdmin(admin.ModelAdmin):
list_display = ('name', 'decade_born_in')

Django - storing logical tests as records

I'm working on a Gran Turismo 5 Django application. Here's a very simplified data model:
class Event(models.Model):
name = models.CharField(max_length=256, unique=True)
class EventCriteria(models.Model):
name = models.CharField(max_length=256, unique=True)
events = models.ManyToManyField(Event)
test = ???
class Country(models.Model):
name = models.CharField(max_length=256, unique=True)
class Make(models.Model):
name = models.CharField(max_length=256, unique=True)
country = models.ForeignKey(Country)
class Car(models.Model):
name = models.CharField(max_length=256, unique=True)
make = models.ForeignKey(Make)
class Setup(models.Model):
name = models.CharField(max_length=256, unique=True)
car = models.ForeignKey(Car)
horsepower = models.IntegerField()
For example, a given event might have the criteria 'Country = Italy'. When applied against the model above, that would require a test like the following:
setup.car.make.country.name == u'Italy'
Does anyone have a good framework for how I might structure the EventCriteria model (especially the 'test' field or fields') to make a) storing these tests and b) applying them as filters in future views possible?
Thanks,
Mike

It's not clear on why your "test" isn't a simple boolean field. The question is confusing.
I'm assuming that really want a persistent filter, since that's often requested.
A Django filter is a dictionary.
SomeModel.objects.filter( column=value, column__contains=value )
SomeModel.objects.filter( **{'column':value, 'column__contains':value} )
You can do this to persist your "test".
Convert your "filter" expression to a dictionary.
JSON-encode the dictionary as a BLOB
Save it.
You can apply your test as follows.
Get the filter BLOB
JSON-decode the dictionary
Use the dictionary in a filter for the appropriate class.