Django: how to choose from a list based on the previous selection?

woojci · August 15, 2021, 3:01pm

Assume that I am a furniture manufacturer. I have many customers and each of them buy from me many diffrent products. In Django I will write class for Customer, Product and the most important for me Order from customer.

How can I do something like filter for that?

class Customer(models.Model):
     name = models.CharField(max_length=10, blank=False)

class Product(models.Model):
    name = models.CharField(max_length=10, blank=False)
    customer_number_product = models.SmallIntegerField(max_length=6, blank=False)
    customer_name = models.ForeignKey(Customer, on_delete=models.CASCADE())

class Order(models.Model):
    order_number = models.IntegerField(max_length=4, blank= False)
    customer_name = models.ForeignKey(Customer, on_delete=models.CASCADE())
    orderdate = datetime...
    deliverydate = datetime...
    ordered_product = HERE IS A PROBLEM

I need to choose from the Product database only one product belongs to specific customer. I do not want to choose from list with thousands products which I sell to all my customers.

KenWhitesell · August 15, 2021, 3:09pm

These are just your definitions for your models. Your various views and forms are responsible for doing whatever filtering is required to build and render the desired page(s).

woojci · August 15, 2021, 3:21pm

But how can I build an instance with these information and in this way, with drop down list with products for one customer? Could you give me any advices?

models.py
class Customer(models.Model):
    name = models.CharField(max_length=10, blank=False)

class Product(models.Model):
    name = models.CharField(max_length=10, blank=False)
    customer_number_product = models.SmallIntegerField(max_length=6, blank=False)
    customer_name = models.ForeignKey(Customer, on_delete=models.CASCADE())

class Order(models.Model):
    order_number = models.IntegerField(max_length=4, blank= False)
    customer_name = models.ForeignKey(Customer, on_delete=models.CASCADE())
    orderdate = datetime...
    deliverydate = datetime...
    ordered_product = models.OneToOneField(Product, on_delete=models.CASCADE())

views.py
def new_order(request):
    form = OrderForm(request.POST or None)
            what sould I write here ? how make a filter for one definition?    
    return render(request, 'new_Order', {'form':form})

KenWhitesell · August 15, 2021, 7:32pm

In your view (new_order), how do you know what customer is requesting the view?

What does your OrderForm look like?

Note - an Order is not a OneToOne relationship with Product, unless the customer may only ever place one order for that product. If the customer is able to place multiple orders for a Product, then it should be a ForeignKey relationship.

Likewise, can a Product only ever be ordered by only one Customer? If so, then you’re ok. But if not - if multiple Customers can place orders for the same product, then you do not want a ForeignKey relationship between Product and Customer. (You probably don’t want a relationship there at all - only between the Order and Customer.)

woojci · September 15, 2021, 9:54am

Hello everyone,
I think that I have found the solution of my problem and now I can nam it - Dependent Cascading Dropdown List. Here is the link to video

BUT (there is also “but” ) I have a problem that it does not work :((((
Please check what I do wrong:

index.html

<!doctype html>
<html lang="en">
<head>
    <!--<meta charset="UTF-8">
    <meta name="viewport"
          content="width=device-width, user-scalable=no, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge"> -->
    <title>Document</title>
    <script src="https://ajax.googleapis.com/ajax/libs/jquery/3.6.0/jquery.min.js"></script>
    <script>
            $(document).ready(function()
            {
                var $select1=$('#select1'),
                    $select1=$('#select2'),
                    $options=$select2.find('option');
                    $select1.on('change',function()
                    {
                        $select2.html($options.filter('[value="'+this.value+'"]'));
                    }).trigger('change');
            });
    </script>

</head>
<body>
    <div style="text-align:center">
        <h2> how to Cerate DDL jQuery Select2</h2>
        <h4>Django Web tutorials</h4>
        <hr/>
        <select id="select1">
            <option selected disabled="true">--Wybierz--</option>
            {% for products in Product%}
            <option value="{{products.id}}">{{products.ksztalt}}</option>
            {% endfor%}
        </select>

        <select id="select2">
            <option selected disabled="true">==wybierz==</option>
            {% for items in Item%}
            <option value="{{items.material_id}}">{{items.wymiar}}</option>
            {% endfor%}
        </select>



    </div>


</body>
</html>

views.py

from django.shortcuts import render
from .models import Material, WymiarMat
# Create your views here.
def magazynddl(request):
	prodobj=Material.objects.all()
	itemobj=WymiarMat.objects.all()
	return render(request, 'Index.html',{"Product":prodobj, "Item":itemobj})

models.py

from django.db import models

# Create your models here.


class Material(models.Model):
    """Tworzę klase do wyboru materiału"""

    DRUT = 1
    TASMA = 2

    KSZTALT = (
        (DRUT, ('Drut')),
        (TASMA, ('Tasma')),
    )
    ksztalt = models.PositiveSmallIntegerField(
        choices=KSZTALT,
        default=DRUT,
        unique=True,
        blank=False,
        null=True,
        help_text='kształt materiału'
    )

    class Meta:
        db_table='materialtab'

    def __str__(self):
        """Ciąg znaków jaki ma reprezentować Obiekt """
        if self.ksztalt == 1:
            cos = 'Drut'
        elif self.ksztalt == 2:
            cos = 'Taśma'
        else:
            cos = 'cos nie trybi'

        return f'{cos}'

class WymiarMat(models.Model):
    """Tworzę wymiary średnicy drutu lub taśmy"""
    material = models.ForeignKey(Material, on_delete=models.CASCADE)
    wymiar = models.CharField('Wymiar',max_length=10, unique=True, blank=False)

    def __str__(self):
        """Ciąg znaków jaki ma reprezentować Obiekt """
        #materialpom=self.material
        #if materialpom =='Drut':
        #    cos = '\u2300'
        #else:
        #    cos = 'gg'
        return f'{self.wymiar}'

obraz

Please do not leave me alone with that

KenWhitesell · September 15, 2021, 11:02am

Without looking at this in too much detail, shouldn’t the second line be $select2=$('#select2'),?

woojci · September 15, 2021, 11:54am

Hehehe It is working I was looking much time at this and movie, and have not seen it :(((
You are my hero.

Could you also give me any website or manual to solve that part of code:

<script>
            $(document).ready(function()
            {
                var $select1=$('#select1'),
                    $select1=$('#select2'),
                    $options=$select2.find('option');
                    $select1.on('change',function()
                    {
                        $select2.html($options.filter('[value="'+this.value+'"]'));
                    }).trigger('change');
            });
    </script>

I do not what happen here ;/

KenWhitesell · September 15, 2021, 12:02pm

I’m not sure I understand what you’re asking here. Are you asking why your original version didn’t work?

If so, I’ll ask you - what’s the value of $select2 at the third line in that section?

woojci · September 15, 2021, 12:32pm

I am sorry, the correct version is as you noted:

<script>
            $(document).ready(function()
            {
                var $select1=$('#select1'),
                    $select2=$('#select2'),    - correct line
                    $options=$select2.find('option');
                    $select1.on('change',function()
                    {
                        $select2.html($options.filter('[value="'+this.value+'"]'));
                    }).trigger('change');
            });
    </script>

My question is about this whole code. How it works step by step, line by line…

e.g. as below I understand that I define the variebles

 var $select1=$('#select1'),
     $select2=$('#select2'),

and what about next lines?

I would like thank you so much for your time and support!!!

I am a beginner and I am still looking for teaching aids. I would like to understand as much as can to change later some code lines e.g. to add one more select3

KenWhitesell · September 15, 2021, 12:34pm

Well, this is all JavaScript code - and I’m going to guess that it’s using jQuery as well. So those would be your resources for further research.
(No, I don’t have any specific recommendations for either.)

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Django: how to choose from a list based on the previous selection?

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