Manually pass files to Django Form

Question

I have a form:

class MessageAttachmentForm(forms.ModelForm):
    class Meta:
        model = MessageAttachment
        fields = ("attachment",)

And in my view, I have it receive some files with the incorrect names so I try to create a new MultiValueDict and submit the files one by one using the correct name like so:

if request.FILES:
    files_dict = request.FILES.copy()
    files_dict.clear()

    for file in request.FILES:
        files_dict["attachment"] = request.FILES.get(file)
        attachment_form = MessageAttachmentForm(files_dict)

        if attachment_form.is_valid():
            attachment = attachment_form.save()
            message_object.attachments.add(attachment)

Where origininally, the request.FILES returns this:

<MultiValueDict: {'attachment0': [<InMemoryUploadedFile: some_image.png (image/png)>], 'attachment1': [<InMemoryUploadedFile: report.pdf (application/pdf)>]}>

And on every iteration of request.FILES, when I add the file to the files_dict, I get this:

<MultiValueDict: {'attachment': [<InMemoryUploadedFile: some_image.png (image/png)>]}>

#And

<MultiValueDict: {'attachment': [<InMemoryUploadedFile: report.pdf (application/pdf)>]}>

Which looks ok, but still doesn't work. I also tried using a regular dict but that was to no avail either.
The attachment_form.errors says that the field attachment is required.

Thank you for taking your time reading this any help is appreciated.

Answer 1

While creating a form instance you need to first pass the post data and then the files. They are positional named arguments:

class BaseModelForm(BaseForm):
    def __init__(self, data=None, files=None, auto_id='id_%s', prefix=None,
                 initial=None, error_class=ErrorList, label_suffix=None,
                 empty_permitted=False, instance=None, use_required_attribute=None,
                 renderer=None):
        ...

source: https://github.com/django/django/blob/master/django/forms/models.py#L280

You need to init your for as following:

        attachment_form = MessageAttachmentForm(files=files_dict)

or this way:

        attachment_form = MessageAttachmentForm(None, files_dict)