Initializing foreignkey in modelform

Question

I'm trying to initialize ForeignKey in a ModelForm. That should be Django 101, but I'm obviously failing at googling and reading docs. This is what I tried:

# models.py

class Sale(models.Model):
    pass

class Settlement(models.Model):
    sale = models.ForeignKey(Sale)

# forms.py

class SettlementForm(ModelForm):        
    class Meta:
        model = Settlement

# views.py

def add_settlement(request, sale_id):
    sale = get_object_or_404(Sale, id=sale_id)

    form = SettlementForm(initial={'Sale': sale})

    form.fields['sale'].initial = str(sale)

    return render(request, 'settlement.html', {'settlementform': form, 'sale': sale})

Yes, that's 2 different (and wrong) ways I tried to initialize ForeignKey, but failed. So, how do you do this the right way?

(yes, I searched StackOverflow, but as I said, I obviously fail at googling :-( )

Answer 1

The thing to remember is that the value of a foreign key field is its ID. Both of those methods can work, but you have (different) issues with each.

For the first method, you should use the correct field name:

form = SettlementForm(initial={'sale': sale.id})

And for the second, you must pass the ID, not the string representation:

form.fields['sale'].initial = sale.id

The first method is preferable though.