django ModelMultipleChoiceField set initial values

Question

I have the following code:

category = forms.ModelMultipleChoiceField(
    label="Category",
    queryset=Category.objects.order_by('name'),
    widget=forms.Select(
        attrs={
            'placeholder': 'Product Category', 'class': 'form-control'}),
    required=True
)

how do I set an initial value in the select box like "Choose a category" so that the select box should have a list of categories with the initial value being "Choose a category"

Answer 1

You can pass it the "initial" setting from your view. For example:

form = FormUsingCategory(initial={'category':querysetofinitialvalues})

The tricky part is that you must have the right queryset. Just like the seed values, it must be of Category.objects.filter(...) - anything else won't work.

Answer 2

If you pass a QuerySet object as an initial value and if widget=forms.CheckboxSelectMultiple, then the check boxes are not checked. I had to convert the QuerySet object to a list, and then the check boxes were checked:

YourForm(
    initial={
        "multi_field": [
            cat for cat in Category.objects.all().values_list("id", flat=True)
        ]
    }
)

Answer 3

Either set initial when you create form instance or set field initial in form init

def __init__(self, *args, **kwargs):
    super(YourForm, self).__init__(*args, **kwargs)
    self.fields["category"].initial = (
        Category.objects.all().values_list(
            'id', flat=True
        )
    )

If you just want to change the text when no field selected you can set empty_label property. https://docs.djangoproject.com/en/1.10/ref/forms/fields/#django.forms.ModelChoiceField.empty_label