I have set a ForeignKey() for class Town in the models file. Ideally, when I select a state, all towns belonging to this state will be listed in town.

#models.py

class State(models.Model):
    state = models.CharField(max_length=50)
    code = models.CharField(max_length=3)
    def __str__(self):
        return self.state

class Town(models.Model):
    town = models.CharField(max_length=50)
    code = models.CharField(max_length=4)
    state = models.ForeignKey(State, on_delete=models.CASCADE)
    def __str__(self):
        return self.town 

Now I can only use all() in queryset to display all towns. I feel like I should use filter(), but I can't find a way to do it。

#forms.py

class Location(forms.Form):

    state = forms.ModelChoiceField( required = True, 
                                    label = "State",
                                    queryset = State.objects.all(),
                                    widget = forms.Select(attrs = {
                                        "class": "form-list-field"}
                                    ))

    town = forms.ModelChoiceField(   required = True, 
                                label = "Town",
                                queryset = Town.objects.filter( ??? ).order_by('town'),
                                widget = forms.Select(attrs = {
                                    "class": "form-list-field"}
                                ))

CodePudding user response：

you can achieve this using

1. Django forms
2. ajax requests

forms.py

    class Location(forms.Form):
    
        state = forms.ModelChoiceField(
            required=True,
            label="State",
            queryset=State.objects.all(),
            widget=forms.Select(attrs={"class": "form-list-field"}),
        )
    
        town = forms.ModelChoiceField(
            required=True,
            label="Town",
            queryset=Town.objects.none(),
            widget=forms.Select(attrs={"class": "form-list-field"}),
        ) # need to populate this using jquery

now write a method in view to returning towns based on selected state

views.py

from django.http import HttpResponse


def get_towns(request, state_id):
    state = State.objects.get(pk=state_id)
    towns = Town.objects.filter(state=state)
    towns_dict = {}
    for town in towns:
        towns_dict[town.id] = town.town
    return HttpResponse(towns_dict, content_type='application/json')

in your html or API code make an ajax request to fetch the list of towns when an state is selected

CodePudding user response：

I already created mini project for achieving those things. It's called dependent drop-down

Plz clone this repo and run it.

Link is here