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Welcome back, everyone, in this lecture, we're going to discuss the Django model form class.

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Now, often we're really using forms to directly interact with a model.

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We've already explored how to create a form that can just accept general information and then we can

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do whatever we want that information.

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But we're often using that to do things like create a new instance of a data point inside a model.

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This is common enough that fortunately, Django provides the model form class, which automatically

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creates a form with fields connected to each model field.

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And you can directly call things like save off of the form, which would save a new instance to your

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models in your database.

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Let's check this all out.

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Insider Code Editor OK, here I am inside Visual Studio Code.

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Here is our form.

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And technically speaking, when somebody submitted this form over in views that pie, we could do whatever

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we wanted with that information through the form.

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Not clean that data dictionary every time someone passed in an actual form.

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I've just been printing it out.

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But technically speaking, I could have done something like save that to a model that already existed

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on the back end.

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However, the reason I didn't really show that too much previously is because if we do plan on using

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forms with models, it makes a lot more sense to use Django's built in model form, a class that is

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going to automatically generate a form based off the fields inside a model.

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Now to do this, we first need a model.

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So we'll come back to explore.

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Open up models that pie inside the cars application, and let's create our first simple model.

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So we'll create a model called a review model.

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So same models thought model inheritance, and we'll just have this be a little simpler than before,

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we'll still accept the first name, so say models, a character field and let's say maxlength a 30.

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Let's also accept a last name for the person giving a review.

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So models again character field maxlength 30 and then just a change it up.

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Let's imagine this time we only want to accept stars like a star rating between one and five stars of

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their experience.

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So we'll create a attribute.

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Stars say models, and let's actually make this one an integer field.

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So we have our model.

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And what I also want to do is register this model inside my administration.

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So how do I do that?

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What I need to do is come to the admin that pi file.

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So I need to open this up and then open up admin that pie.

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And this is where we register a model.

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So I can say something like from that model's import, the review model we made and then register it

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with the admin or say, admin site.

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Register and then register the review model.

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OK, so I've created my model, but technically speaking, I haven't actually really registered it with

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the back end yet because I haven't run migrations for it, so I still need to do that.

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So I'm going to say python managed pie make migrations.

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And what looks like we have an indentation error inside models will come back here, and let's take

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care of that indentation.

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It looks like I had a little space there and everything is off by one space.

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My apologies there.

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OK, now let's save that.

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My background was too dark here.

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Really?

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Actually see that.

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So let's try it again.

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Python managed up pie make migrations perfect, so we initially created that review model.

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Now I'm just going to run the migration.

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So say Python managed pie migrate.

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Perfect.

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So now I should have a car on my actual back end in order to make sure it's actually working, let's

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create a super user so I can access the results from the admin page.

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So we'll say Python managed the pie, create super user.

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And the username, I was going to say, it's my admin email address will be my admin at Edmunds.com.

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Password will be my.

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Admin password.

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As we've mentioned before, it's technically invisible, so we'll enter their password again, my admin.

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Password, hopefully, you didn't mess that up.

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OK, perfect.

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Super user created successfully So now I have a way to actually check on the back end of the fact that

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it was registered there and we actually did some changes.

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So let's first confirm that that is working.

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So I'm going to go to my website and then visit the actual administration view and let's actually run.

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This will say Python managed up pie run server.

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OK, so our server is now running.

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I'm going to open up my Django admin view, so now I should be able to say my username, so my admin

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and then my admin.

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Password.

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I'm going to log in now and tonight I see groups, users, the default authentication authorization,

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but now I also see cars model so I can see reviews.

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And if I wanted to, I could add a manual review here first name, last name and then maybe give it

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some stars.

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So like one, two or five stars.

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Notice right now I can actually go above five stars.

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We're going to talk about errors and validation in the next lecture and customization.

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But for right now, I have, let's say, four stars.

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I can go ahead and save that, and I have my review object.

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OK.

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So obviously, I want the user to be able to provide that within a form.

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So what I could do is go through a very manual process of matching up a custom form here, making sure

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the fields match up and then later on inside of views that by having to make sure that I manually save

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form clean data by actually grabbing those things like, OK, grab the first name and then save that

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to the instance of a model, etc. But luckily for us, because this is so common, Django's already

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thought of something for us.

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So what this is called is a model form.

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How does this work?

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Well, I come back to the forms that file.

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So we'll come back to forms that PI file, and what I'm going to do right now is just comment all this

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out.

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So I'm going to basically not use that review form anymore.

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And instead, I'm going to say from that model's import, my model, which was the review model, then

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I'm also going to say from Let's make sure we don't do that on all caps from.

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Jane, go dot forms.

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Import the model form.

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OK, so this is essentially going to be like forms, but instead of that form, it's forms dot model

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form, but right now I'm just importing it like this so I can just pass in the model form.

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So let's show you how to essentially create a model form, which put simply looks at this model, looks

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at the fields and then will basically automatically generate something that looks like this, which

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automatically generates widgets, which automatically generates a form.

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So we're going to again say class.

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Let's keep the same name review form, so I don't need to worry about import changes later on.

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And now this is going to inherit from model form.

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And then all you need to do here is have a subclass called Meta.

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We say class meta where it has a single attribute for now and we say model is equal to review.

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And that's it, and it's kind of like magic, but really, we can kind of tell what it's doing, all

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it saying is, Hey, I have a model.

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Go ahead and make a form for it.

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So what I would encourage you to do at this point in time is also check out the documentation from this.

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So it's called creating forms from models, and it just talks about the model form and what we discussed

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here.

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Again, super easy.

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You just essentially connect it with model.

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And what you'll also notice is you can actually choose which fields should be represented inside the

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form.

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So if we come back here, we see that we have the attribute model, but maybe you don't actually want

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to collect everything.

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Maybe I only want to collect something like the first name or last name.

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So what I could do is come back to forms.

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So I come back to form that pie here and then say fields as my attribute and you just pass a list of

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the strings you want, such as first name and last name.

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Go ahead and save that change and remember review form that's still being imported over here and review

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form.

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And now I'm still just going to print out my form clean data, and I should be able to see things inside

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my actual rental.

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You.

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And you may have noticed we got a little air here, it says, oh, by the way, you forgot to actually

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create the fields attribute or exclude.

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So it's telling us, Hey, this needs updating.

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I'm going to refresh the page.

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I may need to restart the website if this didn't work.

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So, yeah, let's go ahead and hit control.

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See, that's one of those errors where you just have to rerun the website.

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There we go.

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Python managed up high.

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Go ahead and run that server again.

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And you should see now a very simple rental review form that only accepts a first name and a last name.

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And then if we hit submit query, we see, thank you.

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But notice over here we should see that actually printing out first name and last name.

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Now, obviously, we just connected this to a model.

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So what I could do is come back to forms and say, Hey, when somebody submits this form, actually

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want you to create a new instance of a review.

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Now for that, we should probably add in the stars.

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So we'll say first name.

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Last name.

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And add in stars save that, so now I should see all those fields inside my form.

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So if I come back here and refresh, I see first name, last name and stars, which is an integer field.

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Now, later on, we'll talk about errors and validations and that sort of thing.

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But for right now, I'm going to say first name, last name stars hit submit query and that should say

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thank you.

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And again, we see it printed out here.

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First name, last name stars.

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What you want to do now is save that as a new instance within your models, and then we can go ahead

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and go to admin to check that it's actually all working.

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And luckily for us, it's super easy.

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All we need to do is come back to views.

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And instead of saying something like print a firm, clean data, I just say OK, if that form is valid.

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For example, the length of the names weren't more than 30 characters.

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I simply say form.

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Not safe.

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And this single line, because it's a model form, is going to automatically save what the user passed

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in as a new instance of the model.

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Let's check it out.

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So we'll come back here.

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And remember, I'm still logged in here in my Django admin view with reviews and currently only have

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one review object.

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So we're going to come back to home here.

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And again, I'm going to refresh my rental review form.

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So let's give this a first name.

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The check, I'll say Jose Portela.

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Let's say I had a five star experience.

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I'll go ahead and submit the query.

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It says, thank you.

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And now if I come to the admin page, I'm going to go to reviews.

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No, I have a new review object and it's the one I just applied.

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Jose Portier five stars.

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Perfect.

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So look how easy it is now to let a user directly interact with creating new models.

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So we just need to say the model.

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Then we come to forms and call model form and then underneath class metta.

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You connect it with a model and you connect the fields in that model, you actually want to interact

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with and know how.

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This is why the original form had fields that looked a lot like the model fields like character field

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here was pretty much character field here.

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And what it does is it does a mapping of the model fields to the relevant form fields.

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And if you actually look up in the documentation the model forms, it actually gives you a table of

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what it maps to.

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So if we come back to the Django documentation creating forms for models, you'll see field types.

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Essentially, there are certain model fields that are represented as farm fields.

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So, for example, we can see character field for model field is represented by a character field for

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a form field, and you can see most of them are kind of one to one.

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There's date field eight field email field email field.

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Some don't actually have representation in the form like auto field or big auto field.

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Those are typically used for the primary key index, and that's not something you actually want to represent

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in the form.

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You don't want some user to be able to almost like hack into your database and rewrite primary keys.

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That's why you don't see auto field and big auto field as form fields.

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But here you can see the mapping of the model field and the form field.

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I should also mention there's a ton more information here on again specifying which widgets to use.

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So a lot of it looks kind of similar.

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Again, you're saying widgets, then you say, OK, make this a text area, then make it the attributes,

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etc. There is a little more work you have to do.

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You have to use something called model forms that underscore factory.

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I'll go ahead and let you explore that documentation on your own.

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It's not so bad.

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You basically just come here and create a new model form set.

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Again, it's more and more customization, depending on what you want to do here, for which widgets

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in general we're trying to save ourselves work.

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So often the default choices are good enough for us, but that was the way you could automatically connect

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a model form with a model in the backend, and we just saw that work together.

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Now I want you to keep in mind when we learn about class based views, that's going to give us even

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more power to automatically render an entire web page that specific for creating, reading, updating

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and deleting items from a model.

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So don't think we've kind of reached the pinnacle of Django yet?

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It gets even better kind of all building off of this idea of model forms and the idea that we often

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track website for form on the front end and a model on the back end.

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Coming up next, what I want to talk about are a bunch of other attributes that are going to be useful

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in customizing our model forms.

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But again, I want to make it clear when we're talking about things like how do I use a model form to

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maybe delete an instance for a model or update an instance for a model?

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Well, you can't technically do that with a model form.

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I would highly encourage you to wait until you learn about class based views before you head down that

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direction, because class-based views in the next section are going to make that even easier than using

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model forms.

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So trust me, it gets even better than this, even though this is already pretty darn good.

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So I'll see you in the next lecture when we talk about customizing model forms.