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Django gives us a really handy way to quickly build forms based on our existing models.
Model forms are probably the part of the forms library that you'll use more than any other.
One of the areas of model forms that frustrates people, but is amazingly important, is the requirement to use either fields or exclude. Many people find excludes to be faster, simpler, easier because you don't have to update it every time you change your form or your model. But that's a dangerous decision to make because now any new fields will be automatically added to your displayed form. So use fields instead! Be explicit and control your fields directly by using the fields attribute!
[MUSIC]
0:00
When you give an app a model, it's likely
going to want a form for editing it.
0:04
Django's admin automatically
creates forms for
0:08
creating and editing instances of
our models once we register them.
0:11
But what if we wanna do
it outside of the admin?
0:14
Django provides us with a special
type of form known as a model form.
0:17
A model form is basically
an automatically generated form
0:21
based on a particular model.
0:24
They provide a great easy way to
create new model instances and
0:26
to edit existing ones.
0:29
This means we get all of the goodness
of forms without having to write
0:31
an entire form ourselves.
0:34
So we have our models and we've already
looked at doing standard forms, but
0:36
let's look at doing model forms.
0:40
Model forms are forms that
are made off of our models.
0:42
So we want to do this basically the same
way that we did our suggestion form.
0:46
So that means we want to come here and
we want to add a new file named forms.py.
0:51
And in forms.py, we of course want
to do from django import forms.
0:57
So far, so
exactly the same as it was before.
1:03
All right, so now we need to bring
in our models, so we'll say from.
1:07
import models and now let's go ahead and
make our model forms.
1:11
Let's make a quiz form first,
1:18
this'll show pretty much all the stuff
that we're going to do with a model form.
1:20
We'll say quiz form and
this is forms.modelform,
1:25
thats the one difference right there,
or,the first one rather,
1:30
is that we're going to do model
form instead of just form.
1:33
And then we're not going to specify any
fields because we're just going to use
1:37
the fields that the model gives us but
we're gonna have to specify a class meta.
1:41
So in the class meta we
have specify two things,
1:46
we have to specify the model
which is gonna be models.quiz,
1:50
and then we have to specify fields and
so what fields does,
1:56
there's two things here, and
I'll talk about both of them.
2:01
So there's fields, which we specify
the fields that we want to include.
2:07
So, for our quiz, we want to include
title, description, order, and
2:13
total questions,
cuz those are always there.
2:17
The opposite of this is exclude.
2:21
And if we were doing this with
exclude instead of fields,
2:25
let's come over here and
look at this quiz.
2:29
So we have title, description,
order, course, and total questions.
2:32
So, we might just say okay,
I'm going to exclude course.
2:40
Because course is the one field
that I don't want to exclude.
2:44
This isn't a great idea, and
2:48
I'm gonna cover that in just a little
bit on why that's not a great idea.
2:49
But just so you know that it's there.
2:53
What it does is it basically
leaves off that field.
2:56
That sounds like a great idea,
but there's a little gotcha.
2:59
We'll talk about that in a minute.
3:01
All right, so lets just do our fields and
our model right there.
3:04
Lets go ahead and
actually make a couple more classes.
3:11
Let's do a, I don't think we want
to do a question form because we're
3:16
not going to answer, or we're not
going to create questions directly,
3:20
we are going to create
true false questions.
3:24
Or multiple choice questions.
3:26
So let's create a TrueFalseQuestion form.
3:27
And feel free to use shorter
names on these if you want.
3:34
I tend to like really verbose names,
as you've probably noticed.
3:38
So if you want something that's a little
bit more terse, feel free to do that.
3:44
And we're going to do
TrueFalseQuestion as our model.
3:49
And for fields we want to do order and
3:52
prompt, cuz those are the only
questions we have for true false.
3:56
Or the only options we have for
true false.
4:00
We might want to change
our true false model.
4:03
I'm not going to do it in the course but
you might want to change it so
4:05
that you can just mark on the question
if it's true of if it's false.
4:09
Totally up to you.
4:14
And then for our last one we'll
do multiple choice question form.
4:16
Oops, why did I put question form in here?
4:25
It's not a question form.
4:26
It's a model form.
4:27
Forms.ModelForm.
4:31
Just not thinking things through today.
4:34
So, class Meta and again, model will be
4:36
models.MultipleChoiceQuestion and
4:40
our fields.
4:49
We got a couple of extra fields.
4:51
So we'll do order, prompt,
and shuffle answers.
4:52
And there we go.
5:00
So that is, that's our forms.
5:02
And as you can probably see,
5:06
there's not a whole lot of difference
between our model forms and
5:09
the non-model forms that we created
earlier when we made the suggestion form.
5:13
They're pretty similar,
the main difference is that we do
5:21
this ModelForm thing and we do pretty
much all of our working class meadow.
5:25
We don't specify the fields ourselves.
5:30
Django will take our
fields from our models and
5:33
turn them into the appropriate fields for
a form.
5:36
So we don't have to worry about that
ourselves, which is really, really nice.
5:40
I'm sure you can already see how model
forms save us a significant amount of work
5:45
and coordination.
5:49
We don't have to make sure
that our form fields and
5:50
our model fields line up or,
anything like that.
5:52
One thing that you might be tempted to do,
and I already talked about this a little,
5:56
is to use exclude to leave off
fields that you don't want,
6:00
instead of using fields to include
only the fields that you do want.
6:03
This isn't the best idea though,
6:07
because any field that's not listed in
exclude will be automatically included.
6:08
So you add a new field to your model,
and bam!
6:13
There it is in the form.
6:15
By using the fields attribute,
6:17
you keep your forms stable until you
explicitly add the new field to the list.
6:18
And remember,
explicit is better than implicit.
6:22
Okay, now that we have a couple
of model forms created,
6:26
let's see about using them in our views.
6:29
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