Dropdown with dynamic options in Django form

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I have an expense form that has a field to select the category, but I need the options to be obtained from the database.

These days this is mine forms.py:

from django import forms
from .models import Expense

class ExpenseForm(forms.ModelForm):
    class Meta:
        model = Expense
        fields = '__all__'

In the views.py can create a query to return the categories:

def get_expense_categories():
    with connection.cursor() as cursor:
        cursor.execute(""" select * from units_accountplan;""")

        categories = dictfetchall(cursor)

This table units_accountplan has a simple structure:

id | Category

1 | Petrol

2 | Electricity

You can use this query to fill in the form options, or some other way to do this?

python django form django-templates django-queryset

  • This table is inside Django’s data models or is outside the application?

  • is outside the application, is another Django project that shares the same database, so I can not access directly by model

  • Since it is a database of another application the most appropriate solution would be to create a REST API in the first application providing the table data accountplan, hence recover this data directly in HTML via Javascript (It is that I am considering the fact that one day these two applications may no longer be in the same DBMS).

1 answer

2

Taking into account that the Model of AccountPlan is set within an application your call units within the same database, you would need to do the following in your forms.py:

from django import forms
from .models import Expense
from units.models import AccountPlan

class ExpenseForm(forms.ModelForm):
    accountplan = forms.ModelChoiceField(
        queryset=AccountPlan.objects.all(),
        label='Account Plan',
        widget=forms.Select
    )

    class Meta:
        model = Expense
        fields = '__all__'

Now case the table accountplan is in a different database you can map this second database using multi-db and map the table accountplan as a normal Model Django, taking care to define Meta.managed = False and enter the name of the table in the model. For example:

class AccountPlan(models.Model):
    id = models.BigIntegerField(primary_key=True)
    data = models.DateField(blank=True, null=True)
    descricao = models.CharField(max_length=255, blank=True, null=True)
    nome = models.CharField(max_length=255, blank=True, null=True)

    class Meta:
        managed = False
        db_table = 'units_accountplan'

After this you can use the form as shown above, importing your new Model.

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