Select Boxes and Database

[David Merrick]

Hi. I can put an item from the database into a select box ie Countries of
the World. What I want to know is saying, having chosen New Zealand from
the select box, how do I display all the cities of New Zealand in another
select box.

The database has two tables. First one is Countries. The second table is
cities with populations and the foreign key of Countries table.

Then having chosen Auckland a city in New Zealand I want to display

Country
City
Population

In a template.

I have done this in Php, Javascript and Mysql already.

Cheers Dave


-- 
Dave Merrick

TutorInvercargill

http://tutorinvercargill.co.nz

Daves Web Designs

Website https://tutorinvercargill.co.nz/daveswebdesigns/public_html/

Email merrick...@gmail.com

Ph   03 216 2053

Cell 027 3089 169

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Re: Select Boxes and Database

[Mike Dewhirst]

On 3/12/2023 7:27 am, David Merrick wrote:
Hi. I can put an item from the database into a select box ie Countries 
of the World. What I want to know is saying, having chosen New Zealand 
from the select box, how do I display all the cities of New Zealand in 
another select box.


The database has two tables. First one is Countries. The second table 
is cities with populations and the foreign key of Countries table.


Then having chosen Auckland a city in New Zealand I want to display

Country
City
Population

In a template.

I have done this in Php, Javascript and Mysql already.


Check 
https://simpleisbetterthancomplex.com/tutorial/2018/01/29/how-to-implement-dependent-or-chained-dropdown-list-with-django.html


Also, I recently had a similar task with companies and divisions from 
querysets and had trouble using the form.__init__() method. Here is an 
alternative approach. You can tweak what the form displays by calling a 
form method - here set_division_queryset(). In other words, you can 
populate selection choices based on code elsewhere. In my case I did it 
from within the view code like this ...


# forms.py

class List_Import(forms.Form):

    ...

    division = forms.ModelChoiceField(

    required=False,

    empty_label="Must select a Division",

    queryset=Division.objects.none(),

    ...

    def set_division_queryset(self, divqs):

    self.fields["division"].queryset = divqs




    def clean(self):

    cleaned_data = super().clean()

    selected_division = cleaned_data.get('division')

    available_divisions = self.fields['division'].queryset

    if selected_division not in available_divisions:

    self.add_error('division', 'Invalid choice. Please select a valid 
division.')

    return cleaned_data




# views.py

@login_required(redirect_field_name="next")

@ensure_csrf_cookie

def list_import(request, template="list_import.html", context=None):

    ...

    # User model has get_company() method and Company has get_all_divisions()

    divqs = request.user.get_company().get_all_divisions()

    form.set_division_queryset(divqs)

    ...

    if request.method == 'POST':

    form = List_Import(request.POST, request.FILES)

    # because form.is_valid() needs available_divisions and we are

    # not using form.__init__(), we have to send divqs again

    form.set_division_queryset(divqs)

    if form.is_valid():

    ...



Cheers

Mike





Cheers Dave


--
Dave Merrick

TutorInvercargill

http://tutorinvercargill.co.nz

Daves Web Designs

Website https://tutorinvercargill.co.nz/daveswebdesigns/public_html/
_
_Email merrick...@gmail.com

Ph   03 216 2053

Cell 027 3089 169
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Re: Select Boxes and Database

[Vishesh Mangla]

Hi Mike ,
You can do the following using query parameters.
Create a separate endpoint /getcities?city=... . You send the state and get
array of cities.
This endpoint would give you a json array of cities.
On selection of state on the frontend, your event listener would make api
call to above endpoint and get list of cities without a reload.

Thanks,
Vishesh




On Sun, 3 Dec, 2023, 04:22 Mike Dewhirst,  wrote:

> On 3/12/2023 7:27 am, David Merrick wrote:
>
> Hi. I can put an item from the database into a select box ie Countries of
> the World. What I want to know is saying, having chosen New Zealand from
> the select box, how do I display all the cities of New Zealand in another
> select box.
>
> The database has two tables. First one is Countries. The second table is
> cities with populations and the foreign key of Countries table.
>
> Then having chosen Auckland a city in New Zealand I want to display
>
> Country
> City
> Population
>
> In a template.
>
> I have done this in Php, Javascript and Mysql already.
>
>
> Check
> https://simpleisbetterthancomplex.com/tutorial/2018/01/29/how-to-implement-dependent-or-chained-dropdown-list-with-django.html
>
> Also, I recently had a similar task with companies and divisions from
> querysets and had trouble using the form.__init__() method. Here is an
> alternative approach. You can tweak what the form displays by calling a
> form method - here set_division_queryset(). In other words, you can
> populate selection choices based on code elsewhere. In my case I did it
> from within the view code like this ...
>
> # forms.py
>
> class List_Import(forms.Form):
>
> ...
>
> division = forms.ModelChoiceField(
>
> required=False,
>
> empty_label="Must select a Division",
>
> queryset=Division.objects.none(),
>
> ...
>
> def set_division_queryset(self, divqs):
>
> self.fields["division"].queryset = divqs
>
>
>
> def clean(self):
>
> cleaned_data = super().clean()
>
> selected_division = cleaned_data.get('division')
>
> available_divisions = self.fields['division'].queryset
>
> if selected_division not in available_divisions:
>
> self.add_error('division', 'Invalid choice. Please select a valid 
> division.')
>
> return cleaned_data
>
>
>
> # views.py
>
> @login_required(redirect_field_name="next")
>
> @ensure_csrf_cookie
>
> def list_import(request, template="list_import.html", context=None):
>
> ...
>
> # User model has get_company() method and Company has get_all_divisions()
>
> divqs = request.user.get_company().get_all_divisions()
>
> form.set_division_queryset(divqs)
>
> ...
>
> if request.method == 'POST':
>
> form = List_Import(request.POST, request.FILES)
>
> # because form.is_valid() needs available_divisions and we are
>
> # not using form.__init__(), we have to send divqs again
>
> form.set_division_queryset(divqs)
>
> if form.is_valid():
>
> ...
>
>
>
> Cheers
>
> Mike
>
>
>
>
> Cheers Dave
>
>
> --
> Dave Merrick
>
> TutorInvercargill
>
> http://tutorinvercargill.co.nz
>
> Daves Web Designs
>
> Website https://tutorinvercargill.co.nz/daveswebdesigns/public_html/
>
> Email merrick...@gmail.com
>
> Ph   03 216 2053
>
> Cell 027 3089 169
> --
> You received this message because you are subscribed to the Google Groups
> "Django users" group.
> To unsubscribe from this group and stop receiving emails from it, send an
> email to django-users+unsubscr...@googlegroups.com.
> To view this discussion on the web visit
> https://groups.google.com/d/msgid/django-users/CA%2B%3DMcKYDfzhvQ8ueCKKccYX3gcQUmfoX9NXipqf%3DDipsXPzG7g%40mail.gmail.com
> 
> .
>
>
>
> --
> Signed email is an absolute defence against phishing. This email has
> been signed with my private key. If you import my public key you can
> automatically decrypt my signature and be sure it came from me. Your
> email software can handle signing.
>
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> email to django-users+unsubscr...@googlegroups.com.
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> 
> .
>

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Re: Select Boxes and Database

[Swarup Selvaraj]

Hi David,

The functionality you are interested in is called as *Cascading Dropdown*.

Below are few examples recommended by Bing Chat powered by GPT-4:

   - django-cascading-dropdown-widget · PyPI 
   : This is a 
   package that provides a cascading-dropdown widget for django. It allows you 
   to create a dropdown list that depends on the selection of another dropdown 
   list. It has examples of how to use it with different models and choices 
   generators.
   - How to Create Cascading Dropdown List in Django python 
   
:
 
   This is a tutorial that shows how to create a cascading/dependent dropdown 
   list in django python using jQuery. It has the code for creating the 
   models, views, urls, and template for the application.
   - Django/jQuery Cascading Select Boxes? - Stack Overflow 
   
:
 
   This is a question and answer thread that discusses how to create cascading 
   select boxes in django using jQuery. It has some suggestions of how to use 
   hidden fields, ajax calls, and custom widgets to achieve the desired 
   functionality.
   - Cascading Dropdowns using Javascript - Stack Overflow 
   
:
 
   This is another question and answer thread that explains how to create 
   cascading dropdowns using javascript. It has a simple example of how to use 
   an object to store the options and a function to populate the select 
   elements.


Regards,
SWARUP Selvaraj
On Sunday 3 December 2023 at 01:58:20 UTC+5:30 David Merrick wrote:

> Hi. I can put an item from the database into a select box ie Countries of 
> the World. What I want to know is saying, having chosen New Zealand from 
> the select box, how do I display all the cities of New Zealand in another 
> select box.
>
> The database has two tables. First one is Countries. The second table is 
> cities with populations and the foreign key of Countries table.
>
> Then having chosen Auckland a city in New Zealand I want to display 
>
> Country
> City
> Population 
>
> In a template.
>
> I have done this in Php, Javascript and Mysql already.
>
> Cheers Dave
>
>
> -- 
> Dave Merrick
>
> TutorInvercargill
>
> http://tutorinvercargill.co.nz
>
> Daves Web Designs
>
> Website https://tutorinvercargill.co.nz/daveswebdesigns/public_html/
>
> Email merri...@gmail.com
>
> Ph   03 216 2053
>
> Cell 027 3089 169
>

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