What are Model Forms?

[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