Single Dropdown Selected (Brand) Problem (Product edit/update)

[DTSREPO]

Everything fine but when I try to open product form from product list page, Brand not selected.
Template : backend/prod_form.html
Views : backend/product_view.py
I know it's my problem :(

[SabujXi]

You are creating brands variable in class level. So, that is like creating a static variable where you need to create instance variables. We discussed about this issue a whole day with examples including small discussion in other days. Your code is:

class CrudProduct(View):
    template = 'ecom_app/backend/prod_form.html'
    title = 'Product Form'
    heading = 'Product Form'
    cats = models.Category.objects.all()
    brands = models.Brands.objects.all()
    suppliers = models.Suppliers.objects.all()

    def get(self, request, prod_id=None):

        if prod_id:
            prod_id = int(prod_id)
            prod = models.Product.objects.get(pk=prod_id)
            context = {'prod': prod, 'cats': self.cats, 'brands': self.brands, 'suppliers': self.suppliers,
                       'title': self.title, 'heading': self.heading}
            return render(request, self.template, context)
        else:
            context = {'cats': self.cats, 'brands': self.brands, 'suppliers': self.suppliers, 'title': self.title,
                       'heading': self.heading}
            return render(request, self.template, context)

Look at this part:

class CrudProduct(View):
    template = 'ecom_app/backend/prod_form.html'
    title = 'Product Form'
    heading = 'Product Form'
    cats = models.Category.objects.all()
    brands = models.Brands.objects.all()
    suppliers = models.Suppliers.objects.all()

I told you guys that class level variables are evaluated only once when the interpreter or the system or the module or the class (depending on factors that I discussed with examples) gets loaded. After adding some brands restart the development server with CTRL+C or CTRL+BREAK) and you will see your desired result (brands are in the multiple selection on the product entry form).

So, you can refactor it like below:

class CrudProduct(View):
    template = 'ecom_app/backend/prod_form.html'
    title = 'Product Form'
    heading = 'Product Form'

    def get(self, request, prod_id=None):
        cats = models.Category.objects.all()
        brands = models.Brands.objects.all()
        suppliers = models.Suppliers.objects.all()
        # and the rest goes here

Do the same for post() too.

But if you want to put them in one place then create the __init__ method in the class.

class CrudProduct(View):
    template = 'ecom_app/backend/prod_form.html'
    title = 'Product Form'
    heading = 'Product Form'
    
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self.cats = models.Category.objects.all()
        self.brands = models.Brands.objects.all()
        self.suppliers = models.Suppliers.objects.all()
        # and the rest goes here        
    def get(self, request, prod_id=None):
        # Live in peace here
        ...    

But the later way is not recommended. What if you need a filter with the query inside post or in a later version. Keep your code DRY, but don't be lazy!

@kamruljpi you also take a look at the matter and do not make the same mistake.

To err is human but to avoid such mistakes keep practicing. Keep calm and code with Python. Good luck.

[SabujXi]

@rubelnl @kamruljpi - I told you to refactor the code, give better reasonable names and append a View at the end of view classes. Change CrudProduct to what we discussed about good naming for scalable projects. Refactor other parts too if there are bad things lurking around.

[DTSREPO]

Edited

class CrudProduct(View):
    template = 'ecom_app/backend/prod_form.html'
    title = 'Product Form'
    heading = 'Product Form'

    def get(self, request, prod_id=None):
        cats = models.Category.objects.all()
        brands = models.Brands.objects.all()
        suppliers = models.Suppliers.objects.all()
        if prod_id:
            prod_id = int(prod_id)
            prod = models.Product.objects.get(pk=prod_id)
            context = {'prod': prod, 'cats': cats, 'brands': brands, 'suppliers': suppliers,
                       'title': self.title, 'heading': self.heading}
            return render(request, self.template, context)
        else:
            context = {'cats': cats, 'brands': brands, 'suppliers': suppliers, 'title': self.title,
                       'heading': self.heading}
            return render(request, self.template, context)

Template ...

            <select name="brand" class="form-control">
                <option value="">--- Select Brand ---</option>
                {% with product_brands=prod.brands.all %}

                    {% for brand in brands %}
                        <option value="{{ brand.id }}"
                        {% for b in product_brands %}
                           {% if b.id == brand.id %}
                                selected="selected"
                           {% endif %}
                        {% endfor %}
                        >{{brand.name}}</option>
                    {% endfor %}

                {% endwith %}
            </select>

Not working ....

[SabujXi]

Look at the screenshot, it's working on my machine. Check again!

Let me know if I have missed any other part of your question.

[DTSREPO]

Actually it's not my issue,
I mean when open product form from product list page for update or edit product there not selected my previous saved 'Brands Name',
Like first time i was saved product A, Brand B1
and 2nd times i need to edit this same product and change Brand B1 to Brand B2 but B2 should be selected.
@SabujXi