Fellows,
As my system is becoming complex, I need help to think how to implement complex behavior. I will explain:
I have three models: Purchase, PurchaseDetails, and Stock.
The models is as follows:
class Purchase(models.Model):
def __str__(self):
return self.parceiro_pj.razao_social + ' em ' + str(self.data) + ": " + str(self.soma)
parceiro_pj = models.ForeignKey(ParceiroPJ,blank=True, null=True)
createdat = models.DateTimeField()
data = models.DateField(auto_now=True)
soma = models.DecimalField(max_digits=10, decimal_places=2, default=0.00)
class PurchaseDetails(models.Model):
def __str__(self):
return str(self.parceiro_pj_insumo.insumo.nome) + ' - ' + str(self.quantidade) + ' - ' + str(self.createdat)
purchase = models.ForeignKey(Purchase)
parceiro_pj_insumo = models.ForeignKey(ParceiroPJInsumo)
quantidade = models.IntegerField(blank=False, null=False)
createdat = models.DateField(auto_now=True)
def save(self, *args, **kwargs):
super(PurchaseDetail, self).save(*args, **kwargs) # Call the "real" save() method.
PurchaseDetail.objects.filter(Purchase=self.purchase.id).update(createdat=self.purchase.createdat.date())
itens = PurchaseDetail.objects.filter(compra=self.purchase.id)
valor = 0
for item in itens:
valor = valor + (item.parceiro_pj_insumo.preco * item.quantidade)
no_estoque = Estoque.objects.get(insumo=item.parceiro_pj_insumo.insumo.id)
unidade = Unidade.objects.get(nome=item.parceiro_pj_insumo.insumo.unidade.nome)
qt = no_estoque.quantidade + item.quantidade
volume_peso = no_estoque.volume_peso + (item.quantidade * item.parceiro_pj_insumo.insumo.volume_peso)
Stock.objects.filter(insumo=item.parceiro_pj_insumo.insumo).update(quantidade=qt, unidade=unidade, volume_peso=volume_peso, updatedat=self.purchase.createdat.date())
Purchase.objects.filter(pk=self.purchase.id).update(soma=valor)
Purchase.objects.filter(pk=self.purchase.id).update(data=self.purchase.createdat.date())
class Stock(models.Model):
def __str__(self):
return str(self.insumo.nome) + '(' + str(self.insumo.marca.nome) + ')' + ' - ' + str(self.quantidade)
insumo = models.OneToOneField(Insumo)
quantidade = models.IntegerField(blank=True, null=True)
unidade = models.ForeignKey(Unidade, blank=True, null=True)
volume_peso = models.DecimalField(max_digits=10, decimal_places=2, blank=True, null=True)
updatedat = models.DateField(auto_now=False, blank=True, null=True)
There are related:
a) One Purchase has Many PurchaseDetails; b) Every PurchaseDetail has an effect on Stock. For every PurchaseDetail operation (insert, change, delete) the Stock must be updated.
I figure it out how to make the change on Stock every time a PurchaseDetail is inserted. But for the DELETE and UPDATE, the logic seems to be much more complex.
If I edit PurchaseDetails, the way its made, if I already had an item in the database, it will be calculated again when I save the PurchaseDetails (this model is embbeded with the Purchase form at admin), causing error and updating again the Stock.
I dont know how to implement the right way of doing it.
I have to check if its a new item on PurchaseDetail, or if it is a already existent register before update Stock, I dont know how to do it. Also, I dont know hot tom implement the case when I have to delete PurchaseDetails, and decrease items on Stock.
Anyone can help, please?
You may consider exploring the functionality provided by Django signals, which will provide you with a nice way to implement this type of behavior. Signals can be sent by built-in model methods like __init__() and save(), and are useful when different areas of your application might want to use information about these types of events.
Some of Django's built-in signals include pre_save, post_save, pre_delete, post_delete, etc; it is also straightforward to define and send your own signals.
Looking at a simplified example of what you already have, lets say you wanted to update a particular Stock every time a related PurchaseDetail was saved, for some reason. You might define a method like:
def update_stock(sender, instance, **kwargs):
purchase_details_id = instance.id
# do something here, like update and save a stock
post_save.connect(update_stock, sender=PurchaseDetail)
update_stock is the receiver function which will be called after the save of the PurchaseDetail object.
For further reference:
https://docs.djangoproject.com/en/1.10/ref/signals/
Related
I have two models Bill and Payment each with 3 fields. Here I want to update field last_price directly when user pay bill. If user pay complete amount then it would be 0. or if user not pay complete amount then remaining amount want to be save in last_price. So here I want to update amount of last_bill directly when user pay bill.
Note: Both models are in separate app
My Fields are:
BillApp/models
Bill(model.Model):
bill_no = models.IntegerField(max_length = 100,primary_key=True)
last_price = models.IntegerField()
Name = models.CharField(max_length = 20)
PaymentApp/models
Payment(model.Model):
id = models.CharField(max_length = 100,primary_key=True)
bill_no = models.ForeignKey(Bill, on_delete = SET_NULL,null=True)
total_amount = models.CharField(max_length = 10)
def save(...):
Update value of Bill.last_price
How do I update value of Bill.last_price in the save method
I tried this for update field last_price
def save(self,*args, **kwargs):
new_last_price = self.total_amount - self.bill_no.last_price
print("new_last_price : ",new_last_price)
bill_detail = Bill.objects.filter(bill_no=self.bill_no).first()
print("bill_detail : ",bill_detail)
try:
with transaction.atomic():
updated_field = bill_detail.save(update_fields = ['last_price'])
print("updated_field : ", updated_field)
super().save(*args, **kwargs)
print(Bill.objects.filter(bill_no=self.bill_no).first().last_price)
except IntegrityError:
print('Exception in save')
I getting correct output of new_last_price and bill_detail..
but updated_field display None ..
How Can I save new value in Bill?
Your save method will save the data and refresh the object instance but will not return the object instance. Use directly show last price.
bill_detail.save(update_fields = ['last_price'])
print(bill_detail.last_price)
i have this model
class Person(models.Model):
picture = models.ImageField(
default='default.jpg', upload_to='profile_pics', )
firstName = models.CharField(blank=True, max_length=100)
familyName = models.CharField(blank=True, max_length=100)
age = models.IntegerField(default=0)
GENDER = [
("M", 'Male'),
("F", 'Female'),
("U", 'UNKNOWN'),
]
gender = models.CharField(
max_length=2,
choices=GENDER,
default="U",
)
address = models.CharField(blank=True, max_length=100)
remark = models.TextField(default="no remark")
description_vector = models.TextField(blank=True)
i want to infer the description_vector from the picture field (with a method called identifie(pictur) that return a string ) whenever i add a new Person or changing a model image (if the image didn't change i dont want to change the description_vector)
i know i can use the save method like here but i dont know how to specify that when the image change the vector change.
i dont know if it changes anything but i use django-rest-framowrk to add and change persons
i know
I am not sure I understand what your specific doubt is, but I think this might be helpful.
def save(self, *args, **kwargs):
if self.id is not None: # check only when update
original_picture = self.objects.get(id=self.id).picture
if original_picture !== self.picture # You must add here your method to evaluate if both images are equal
self.vector = some_method_to_change_vector(self.picture)
return super().save(*args, **kwargs)
I have a very big model in models.py:
simplified version is:
class MyModel(models.Model):
item_1 = models.FloatField(null=True, blank=True)
...
item_20 = models.FloatField(null=True, blank=True)
in views.py:
def form_valid(self, form_class):
instance = form_class.save(commit=False)
for i in range(1, 20):
name = 'item_' + str(i)
instance.name = i
With this the field name 'item_1' ... to 'item_20' in instance is not recogniced. Instead 'name' is added to instance like other new field...
How can I iterate and save my model?
Any suggestion?
Thanks!!!
You should probably use setattr in order to loop through the fields and set the values in them. Try this:
def form_valid(self, form_class):
instance = form_class.save(commit=False)
for i in range(1, 20):
name = 'item_' + str(i)
setattr(instance, name, value) # Where value is the data you wanted to save in the field `name`
Similary user getattr() to get the data by looping through the class instance.
Using Django, I am creating a database that will keep track of unanswered posts in forum and if/what employee(operator) is assigned to that post.
Models Operator and ThreadVault are permanent while Thread is intermediate/temp.
I will be making a api call to the forums to get a list of the unanswered posts once every ten minutes. I will then check to see if the thread ID already exists in the model ThreadVault. If not, it will add it to ThreadVault. Then, I will have a temporary/intermediate table Thread that will contain the unanswered posts for the past 10 minutes. After every 10 minutes, the table Thread will clear out and refresh with a new batch of unanswered threads.
A operator/employee may or may not be assigned to the thread. To do this, I am having ThreadVault operator_user_name point to Operator model.
class Operator:
operator_ldap = models.ForeignKey(settings.AUTH_USER_MODEL,
related_name='operator_requester')
operator_irc_name = models.CharField(max_length="25")
operator_user_name = models.CharField(max_length="25")
class ThreadVault:
thread_id = models.CharField(max_length="50")
url = models.CharField(max_length="200")
operator_user_name = models.ForeignKey(Operator) ## Can be Empty
#intermediate table
#Thread model clears out once every
#10 minutes when API repopulates data
class Thread:
url = models.ForeignKey(ThreadVault)
author_username = models.CharField(max_length="50")
author_name = models.CharField(max_length="50")
thread_id = models.ForeignKey(ThreadVault)
forum_id = models.CharField(max_length="50")
subject = models.CharField(max_length="200")
reply_count = models.CharField(max_length=("3"))
latest_post_date = models.CharField(max_length=("50"))
operator_user_name = models.ForeignKey(ThreadVault) ## Can be Empty
I know at this point I am not doing this correctly. How can I do this?
This worked out perfect:
class Operator(models.Model):
operator_ldap = models.ForeignKey(settings.AUTH_USER_MODEL,
related_name='operator_requester')
operator_irc_name = models.CharField(max_length="25",
blank=True, null=True)
operator_user_name = models.CharField(max_length="25",
blank=True, null=True)
class ThreadVault(models.Model):
thread_id = models.CharField(max_length="50")
url = models.CharField(max_length="200")
operator_user_name = models.ForeignKey(Operator, blank=True, null=True) ## Can be Empty
#intermediate table
#Thread model clears out once every
#10 minutes when API repopulates data
class Thread(models.Model):
url = models.ForeignKey(ThreadVault,
related_name="url_vault")
author_username = models.CharField(max_length="50")
author_name = models.CharField(max_length="50")
thread_id = models.ForeignKey(ThreadVault,
related_name="thread_vault")
forum_id = models.CharField(max_length="50")
subject = models.CharField(max_length="200")
reply_count = models.CharField(max_length=("3"))
latest_post_date = models.CharField(max_length=("50"))
operator_user_name = models.ForeignKey(ThreadVault,
related_name="operator_user_name_vault",
blank=True, null=True) ## Can be Empty
I have 2 models:
Category(models.Model):
name = models.CharField(max_length=30)
no_of_posts = models.IntegerField(default=0) # a denormalised field to store post count
Post(models.Model):
category = models.ForeignKey(Category)
title = models.CharField(max_length=100)
desc = models.TextField()
user = models.ForeignKey(User)
pub_date = models.DateTimeField(null=True, blank=True)
first_save = models.BooleanField()
Since I always want to show the no. of posts alongwith each category, I always count & store them every time a user creates or deletes a post this way:
## inside Post model ##
def save(self):
if not pub_date and first_save:
pub_date = datetime.datetime.now()
# counting & saving category posts when a post is 1st published
category = self.category
super(Post, self).save()
category.no_of_posts = Post.objects.filter(category=category).count()
category.save()
def delete(self):
category = self.category
super(Post, self).delete()
category.no_of_posts = Post.objects.filter(category=category).count()
category.save()
........
My question is whether, instead of counting every object, can we not use something like:
category.no_of_posts += 1 // in save() # and
category.no_of_posts -= 1 // in delete()
Or is there a better solution!
Oh, I missed that! I updated the post model to include the relationship!
Yes, a much better solution:
from django.db.models import Count
class CategoryManager(models.Manager):
def get_query_set(self, *args, **kwargs):
qs = super(CategoryManager, self).get_query_set(*args, **kwargs)
return qs.annotate(no_of_posts=Count('post'))
class Category(models.Model):
...
objects = CategoryManager()
Since you didn't show the relationship between Post and Category, I guessed on the Count('posts') part. You might have to fiddle with that.
Oh, and you'll want to get rid of the no_of_posts field from the model. It's not necessary with this. Or, you can just change the name of the annotation.
You'll still be able to get the post count with category.no_of_posts but you're making the database do the legwork for you.