Django Advantage forms.Form vs forms.ModelForm

Question

There is a question very similar to this but I wanted to ask it in a different way.

I am a very customized guy, but I do like to take shortcuts at times. So here it goes.

I do find these two classes very similar although one "helps" the programmer to write code faster or have less code/repeating code. Connecting Models to Forms sounds like an obvious thing to do. One thing that is not particularly clear in the docs using a ModelForm. What happens if you need to add extra fields that are not in the Model or some way connected to another Model?

I guess you could subclass that out and make it work, but does that really help you save time than just manually doing it with a Form?

So next question may not have a definite answer if I do subclass it out, and use ModelForm. Is ModelForm particularly faster than Form? Does it still use the same Update techniques or is binding significantly faster in one or the other?

Answer 1

If you want a form across two models, you got a couple options:

1) create two modelforms, save each individually when posted, and if one of the two depends on the other (i.e. foreignkey), set that in your view before saving.

2) try Django's inline formset: http://docs.djangoproject.com/en/dev/topics/forms/modelforms/#using-an-inline-formset-in-a-view

3) Add non-model fields to your modelform. On a ModelForm, you can add fields that are not tied to your model. They are available in cleaned_data as any other field would, be but are simply ignored when the model is saved.

One advantage that ModelForm's have over Form's is you can specify the ordering of fields (searching for how to order Form fields brought to your post incidentally). Obvious other advantages are you don't have to rewrite your model saving code