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- [Instructor] Hi, and welcome back.

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In this video, we're
going to be using Models.

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Now, we have a Resources
folder and a Models folder.

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Apologies, packages.

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And in the Resources package,

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we've got the Item file
which contains two classes,

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Item and Item list down here.

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And they're both resources

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which means they both belong in here,

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inside the Resources package.

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However, the User file contains a class

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which is not a resource as well
as one which is a resource.

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So, what we're gonna do is
we're going to move this class

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our of this file seeing as
it doesn't belong there,

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even though everything
works if it is there,

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but it just doesn't make sense
from a logical point of view,

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so what I've done is
I've cut that class out

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and we're going to
create a new file inside

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the models folder, call it User.py

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and paste that thing in there.

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So, that's our class which
we've essentially just moved

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from the resources package
to the models package.

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Now, we have to remember to
import the things that we need,

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which are gonna be sqlite3 only.

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So, I'm gonna save User.py in resources

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and go back to the models
and import sqlite3.

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Now, we need sqlite3
because the find_by_username

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and find_by_ID methods in
the User class use sqlite3.

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So, let me just take a moment to explain

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what a model is because
up until now we've thought

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of our resource as things
that the API responds with,

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things that API clients can
ask for, and things like that.

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And that is true, that's
what a resource is.

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And essentially a resource
is what the API thinks of.

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The API deals with
resources such as Users,

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items, stores, students,

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basically similar to object
oriented programming.

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So, our class User here is not a resource

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because the API cannot
receive data into this class

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or send this class as
a JSON representation,

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things like that.

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This class here is a helper essentially.

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It is a helper that we
use to store some data

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about the User and also a
helper that contains a couple

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of methods that allow
us to easily retrieve

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User objects from a database.

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So, that's what a model is.

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A model is our internal
representation of an entity.

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Whereas a resource is the external

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representation of an entity.

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Our API clients, like a
website or a mobile app,

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think they're interacting with resources,

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that's what they see.

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And when our API responds
it responds with resources.

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Again, that's what the client sees.

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However, when we deal internally
in our code with a User,

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for example in our security.py file,

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we are using find by Username for example.

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We're not using the resource,
we're using the model

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because that's what gives us the power

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and that's what has the code
that allows our programme

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to do what it has to do.

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So, the model essentially is a helper

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that allows our programme or
that gives us more flexibility

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in our programme without
polluting the resource,

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which is what the clients interact with.

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So, models and resources
are reasonably separate

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although they can be linked
in the case of our User

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register and our User model.

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If you go to the User
register, for example,

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we had the User.find_by_Username
method there,

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which means that this
resource is using the model

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and to get some data out.

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Okay, now that we've determined
the difference between

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a model, which is our
internal representation,

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and the resource, which is
the external representation,

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it makes sense to rename
the class to be UserModel

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instead of User.

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Okay?

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So, I'm going to copy the name

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because we're gonna be
changing this reference in

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a bunch of places.

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For example, in the user.py
file inside the Resources folder

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we're going to have to
import UserModel from

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the models.user file

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and then in any instance where
we used to use the user class

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now we have to change that to UserModel.

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Remember, we've not
changed any functionality,

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all we've done and once
again is moved things about

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to make things a little
easier to understand.

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Okay, so we used the User
file there and that's it.

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And if you wanna make
sure you can press Ctrl+F

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on Windows or Cmd+F on Mac

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and that in Atom allows you to find.

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And so just type User there
and then you'll be able to see

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that at no point the User class is used.

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So, then you press Escape
and that leaves that bit.

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So, in order to save this file

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and then also let's go
into the security.py file

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and change the input from
resources.user to models.user

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and from User to UserModel.

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And once again here use the User class,

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we're gonna change that.

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And down here we also use it
we're gonna change it, too.

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Remember, even though we've
renamed the class to UserModel

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the variables don't have to change.

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It's a UserModel class
that we're accessing,

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but really what it's
returning is a User entity.

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It just so happens that
it's the internal entity

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as opposed to the external
entity that we're dealing with.

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Okay?

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Ow that we've updated the
User to be a UserModel,

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let's do the same with the item.

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So, let's close these tabs here

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and create a new file
inside the Models folder

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and call it item.py.

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Remember you can call these
files whatever you want,

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it just makes sense
because there's going to be

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an item model to be in the models package

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and be called item.

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But if you think if you'd
rather call it item_model,

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for example, you can do that.

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Now, okay, so then what we
have to do here is not move

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because we don't have a
currently existing item model,

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but we're going to create an item model.

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Remember, this is the internal
representation if what

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an item does and looks like.

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So, let's go into the item resource

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and find out what things
we do in the item resource

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that could be done by a model.

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I immediately spot something that may not

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belong in a resource.

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Remember the resource
is used to map endpoints

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such as the get verb and the post verb

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and to the /item/name.

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And we've got a get,
post, delete, and put,

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but we also have a couple
of other methods here

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that maybe don't belong in our resource

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because the clients don't interact

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with these methods directly.

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An example of that is
this find_by_name method.

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And another example may
be this insert method.

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These two are not called
by an API directly,

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they are only used from within our code,

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so therefore it doesn't make
sense to pollute the resource

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with these methods because
it doesn't help at all.

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It makes more sense to move them elsewhere

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so that the resource is
only containing methods

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that the API interact with.

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Why?

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Just because it makes things
easier in the longterm

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for us to modify the code.

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If we go in here and we see
get, post, delete, and put,

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we know that anything we
change is gonna change our API.

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Whereas, if we change this insert method

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that's not gonna change our API,

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but it may modify the way our code works.

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Okay?

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So, let's go back into
item.py in the Models folder

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and let's import sqlite3
because we need that

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and then create the class ItemModel.

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Also remember the item model
is our internal representation,

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so it also has to contain
the properties of an item

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as object properties.

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So, for that we're going
to create an _init_ method

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and every item has a name and a price,

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so we're going to out
those in this argument

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and self.name = name, self.price
= price there as well.

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Okay, now I'm also going
to create a JSON method

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and all this is going to
do is it's going to return

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a JSON representation of the
model, basically a dictionary.

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Okay?

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So, that is a dictionary
representing our item.

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Every item contains a name and a price,

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so that's what our
dictionary contains, too.

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Now, the next steps are
to move all of the methods

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from the item resource
that don't belong there

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into the item model.

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Now, I'm sure that you can do that,

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I'd recommend you pause the
video and give that a go

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and then we'll do that here as well.

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Okay, hopefully you got that.

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I'm going into the item resource

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and I'm going to just cut
everything that doesn't belong.

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So, I'm going to cut
this class method there

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and I'm going to put it in here.

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And then I'm going to
cut this insert method

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that doesn't belong and
I'm going to put it here.

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Make sure the indentation
is always correct

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and so nothing is indented
more or less than it should be.

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And finally there is also
a cheeky method there

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that's also a bit hidden,
the update method,

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we're going to cut that and
put it down here as well, okay.

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Just as an aside, methods
within a class should be

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separated by a new line, so
as you can see this method

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and this method are
separated by a new line,

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but classes within a file
should be separated by two

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new lines, that's just sort
of a Python coding standard.

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No problem if you don't do that,

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but that's just the convention.

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Now, in all the places where
we used self.find_by_name

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we have to change that
to use the item model.

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So, let's go to the very top
and import the ItemModel.

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So, from models.item import ItemModel

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and then we're just gonna
change every instance

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of self for ItemModel
where appropriate remember.

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Okay, so we've got find_by_name,
find_by_name, insert,

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and then we have there's
delete method there,

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that's part of the API so nothing there.

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We've got self.find_by_name,
that's now in the ItemModel,

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self.insert and self.update.

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Okay?

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Which is quite interesting.

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So, what else?

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Well, now that the ItemModel
here is worried about

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essentially itself and
what I mean with that is

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this ItemModel is the item
that we are dealing with.

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So, we can create an new
ItemModel that stores

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a name and a price.

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And that creates an object that has

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those two properties in it.

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So, does it make sense for the ItemModel

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to have a class method insert?

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And now, what I mean with that is

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we have the ItemModel,
which represents an item,

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and this insert method
is taking in an item

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that it is going to
insert into the database.

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Would it not make sense for
this to not be a class method

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and for it just to use
self since essentially

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that's what it's doing,
it's inserting itself?

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Previously, for example,
in the resources file

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we would call this
itemModel.insert the updated_item,

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but it makes sense for us
to do updated_item.insert.

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And that that does is that
saves the item to the database.

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So, lets do just that.

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Let's go back into the model
and change the insert to model,

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the insert method to self,

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and the update method to
self as well, and of course,

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in the cursor we have to
make sure to use self.name.

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Remember, self is now an
object and not a dictionary,

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so we can access these
properties as we would in any

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other object as well.

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Okay.

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The find_by_name method, however,

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should still be a class method

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because it is gonna return
an object of ItemModel

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as opposed to a dictionary.

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So, what we're gonna do in
here is instead of returning

249
00:14:23,419 --> 00:14:25,487
a dictionary we're going to return

250
00:14:25,487 --> 00:14:28,339
an object of type ItemModel.

251
00:14:28,339 --> 00:14:31,190
This is a class method,
which means it has CLS,

252
00:14:31,190 --> 00:14:33,130
which is a reference to the class.

253
00:14:33,130 --> 00:14:36,756
So, can you modify this
code so that it returns

254
00:14:36,756 --> 00:14:40,923
an object of type ItemModel
instead of a dictionary?

255
00:14:46,944 --> 00:14:48,035
I'm sure you got it.

256
00:14:48,035 --> 00:14:51,368
All we have to do is make sure to do CLS

257
00:14:52,278 --> 00:14:54,528
and then row[0] and row[1].

258
00:14:55,833 --> 00:14:59,018
And once again what that does
is CLS calls the ItemModel

259
00:14:59,018 --> 00:15:01,513
in its method, row[0] Was the name,

260
00:15:01,513 --> 00:15:04,071
which goes into the name argument,

261
00:15:04,071 --> 00:15:07,045
row[1] Was the price , which
goes into the price argument

262
00:15:07,045 --> 00:15:10,462
and that gives us a new ItemModel object.

263
00:15:11,364 --> 00:15:15,996
Of course, row[0] also happens
to be the first parameter

264
00:15:15,996 --> 00:15:18,048
the parameter number zero,

265
00:15:18,048 --> 00:15:19,892
and row[1] also happens to be

266
00:15:19,892 --> 00:15:22,740
the second parameter number one.

267
00:15:22,740 --> 00:15:26,567
So, this is a perfect scenario
for us to use our argument

268
00:15:26,567 --> 00:15:28,067
unpacking like so.

269
00:15:30,528 --> 00:15:32,558
And once again, that does exactly the same

270
00:15:32,558 --> 00:15:35,862
it just passes each of the arguments

271
00:15:35,862 --> 00:15:39,258
or each of the elements
in the row to a parameter

272
00:15:39,258 --> 00:15:42,110
and delete method in turn.

273
00:15:42,110 --> 00:15:46,688
So, that just simplifies
the code just a bit more.

274
00:15:46,688 --> 00:15:50,195
Okay, so now that we've saved this,

275
00:15:50,195 --> 00:15:52,501
let's go back into our resources

276
00:15:52,501 --> 00:15:56,837
and now we're gonna make a
few changes here as well.

277
00:15:56,837 --> 00:16:00,254
Okay, remember the ItemModel.find_by_name

278
00:16:02,391 --> 00:16:06,558
now returns an item object
as opposed to a dictionary

279
00:16:08,681 --> 00:16:11,528
and that means that we cannot return item

280
00:16:11,528 --> 00:16:13,093
because that's an time object,

281
00:16:13,093 --> 00:16:15,522
an ItemModel object as
it was to a dictionary,

282
00:16:15,522 --> 00:16:18,939
so we have the return is item.json, okay.

283
00:16:28,559 --> 00:16:32,559
And what that's gonna
return is the item itself.

284
00:16:35,406 --> 00:16:38,342
Down here that's fine because
that's not returning anything.

285
00:16:38,342 --> 00:16:42,264
And here we've got an
item that is a dictionary.

286
00:16:42,264 --> 00:16:43,922
What we're gonna do is make sure that this

287
00:16:43,922 --> 00:16:47,957
is not a dictionary,
but an ItemModel object.

288
00:16:47,957 --> 00:16:51,485
So, what to do is just say ItemModel,

289
00:16:51,485 --> 00:16:53,402
name and price like so,

290
00:16:54,779 --> 00:16:56,636
and now that we've got an ItemModel

291
00:16:56,636 --> 00:16:59,106
this can be inserted into the database

292
00:16:59,106 --> 00:17:03,273
so we can change this thing
here to be item.insert.

293
00:17:04,672 --> 00:17:07,804
And that's just slightly easier

294
00:17:07,804 --> 00:17:12,297
because it doesn't
needlessly call the class

295
00:17:12,297 --> 00:17:14,547
instead of the item itself.

296
00:17:15,549 --> 00:17:19,716
Okay, down here once again
the time is a item object,

297
00:17:23,816 --> 00:17:26,978
the updated item is a item dictionary.

298
00:17:26,978 --> 00:17:29,723
So, what we have to do is
make sure that the object item

299
00:17:29,723 --> 00:17:32,140
is also an ItemModel like so.

300
00:17:39,346 --> 00:17:42,888
And then we have here
that if the item is a none

301
00:17:42,888 --> 00:17:45,487
means that we didn't find
an item in the database.

302
00:17:45,487 --> 00:17:47,976
We want to insert the updated item,

303
00:17:47,976 --> 00:17:50,643
so we can do updated_item.insert

304
00:17:53,204 --> 00:17:56,492
and if the item was none
that means that the,

305
00:17:56,492 --> 00:17:58,178
sorry if the item was not none,

306
00:17:58,178 --> 00:18:00,168
that means that the item was there.

307
00:18:00,168 --> 00:18:04,335
So, what we're going to do
is say updated_item.update.

308
00:18:07,668 --> 00:18:10,995
And remember, all that's
gonna do is return

309
00:18:10,995 --> 00:18:13,480
or rather update the database with

310
00:18:13,480 --> 00:18:15,647
the updated item's values.

311
00:18:16,769 --> 00:18:18,980
And finally, instead of
returning updated_item

312
00:18:18,980 --> 00:18:22,580
make sure to return updated_item.json.

313
00:18:22,580 --> 00:18:26,374
Now, I appreciate that
this looks a bit strange

314
00:18:26,374 --> 00:18:31,234
because the item is the one
we found in the database.

315
00:18:31,234 --> 00:18:33,484
Updated_item is a new item.

316
00:18:34,526 --> 00:18:38,431
So, surely we cannot
update the updated_item

317
00:18:38,431 --> 00:18:40,945
because that's not in the database,

318
00:18:40,945 --> 00:18:43,112
that item we just created.

319
00:18:43,946 --> 00:18:46,529
Surely we should do item.update

320
00:18:47,455 --> 00:18:51,917
so that we can update the
item with some new values.

321
00:18:51,917 --> 00:18:52,952
And I agree.

322
00:18:52,952 --> 00:18:55,981
I agree with you that this
is slightly more confusing

323
00:18:55,981 --> 00:18:57,586
than it should be.

324
00:18:57,586 --> 00:19:00,140
We're going to change
that in this section.

325
00:19:00,140 --> 00:19:03,257
However, remember we're
dealing with code here

326
00:19:03,257 --> 00:19:04,424
and not logic.

327
00:19:06,184 --> 00:19:10,303
The item is something we've
retrieved from the database,

328
00:19:10,303 --> 00:19:13,879
but this item isn't a row of a database,

329
00:19:13,879 --> 00:19:16,516
this item is an ItemModel.

330
00:19:16,516 --> 00:19:18,611
So, when we find it in the database,

331
00:19:18,611 --> 00:19:21,778
this item here is just a Python entity

332
00:19:22,926 --> 00:19:24,867
that contains a name and a price.

333
00:19:24,867 --> 00:19:26,284
That's all it is.

334
00:19:27,296 --> 00:19:30,845
This updated_item is another ItemModel,

335
00:19:30,845 --> 00:19:33,903
which contains a name,
presumably the same name,

336
00:19:33,903 --> 00:19:36,486
and possibly a different price.

337
00:19:38,675 --> 00:19:42,799
If we call item.update all
that's gonna do is it's going

338
00:19:42,799 --> 00:19:46,966
to go to the ItemModel
update with the item ask self

339
00:19:48,467 --> 00:19:51,973
and then it's going to
call this query here

340
00:19:51,973 --> 00:19:55,476
with the items.price and the items.name.

341
00:19:55,476 --> 00:19:57,878
Now, that's not going to change anything

342
00:19:57,878 --> 00:20:02,016
because that item is
already in the database.

343
00:20:02,016 --> 00:20:04,953
If we call updated_item.update,

344
00:20:04,953 --> 00:20:07,803
that doesn't make sense for us logically,

345
00:20:07,803 --> 00:20:10,773
but all that's going to
do is it's going to get

346
00:20:10,773 --> 00:20:15,031
the updated_items
properties in here itself

347
00:20:15,031 --> 00:20:17,847
and then it's going to
execute this equal query

348
00:20:17,847 --> 00:20:19,488
with that item's properties,

349
00:20:19,488 --> 00:20:22,605
which in turn is going to update the item

350
00:20:22,605 --> 00:20:25,331
that already is in the database.

351
00:20:25,331 --> 00:20:29,982
So, remember there is a big
disconnect between our database

352
00:20:29,982 --> 00:20:31,466
and our Python code.

353
00:20:31,466 --> 00:20:34,617
These two items here even
though one of them we retrieve

354
00:20:34,617 --> 00:20:37,131
from the database and the other we didn't,

355
00:20:37,131 --> 00:20:39,771
essentially act on the same row,

356
00:20:39,771 --> 00:20:42,242
which is very, very weird.

357
00:20:42,242 --> 00:20:44,022
And but, we're going to improve that,

358
00:20:44,022 --> 00:20:46,212
so don't worry about it too much

359
00:20:46,212 --> 00:20:50,945
and because we are going
to make things better.

360
00:20:50,945 --> 00:20:53,794
Okay, so this video
was gettin' pretty long

361
00:20:53,794 --> 00:20:56,409
and so I think that's
everything for this video.

362
00:20:56,409 --> 00:21:00,939
Let's make sure that we've not
missed any part of the code

363
00:21:00,939 --> 00:21:03,281
or like any missing imports
and things like that,

364
00:21:03,281 --> 00:21:05,930
but it's also very important.

365
00:21:05,930 --> 00:21:07,347
This is all fine.

366
00:21:09,402 --> 00:21:11,625
We've imported the ItemModel

367
00:21:11,625 --> 00:21:14,682
and we're using that everywhere

368
00:21:14,682 --> 00:21:17,649
and every item we are returning item.json

369
00:21:17,649 --> 00:21:21,851
as opposed to the item itself
except in the post method.

370
00:21:21,851 --> 00:21:25,985
So, this seems like an
important thing to do.

371
00:21:25,985 --> 00:21:28,424
And in the post method we
were returning just item

372
00:21:28,424 --> 00:21:30,605
as opposed to item.json

373
00:21:30,605 --> 00:21:33,400
and make sure that you're returning .json.

374
00:21:33,400 --> 00:21:35,131
If not, your API will not work

375
00:21:35,131 --> 00:21:37,637
because it cannot return item objects

376
00:21:37,637 --> 00:21:40,491
it can only return dictionaries.

377
00:21:40,491 --> 00:21:44,128
Okay, and this is not
returning anything, really.

378
00:21:44,128 --> 00:21:47,428
Well, it's returning a message,
not dealing with any items,

379
00:21:47,428 --> 00:21:49,164
so that's fine.

380
00:21:49,164 --> 00:21:51,976
And all of these things are fine as well

381
00:21:51,976 --> 00:21:54,612
and we are returning JSON there

382
00:21:54,612 --> 00:21:57,779
and the ItemList class it doesn't use,

383
00:21:59,199 --> 00:22:02,491
well we're not gonna change that just yet.

384
00:22:02,491 --> 00:22:04,560
We'll change that in the next video.

385
00:22:04,560 --> 00:22:06,825
And so that's all fine.

386
00:22:06,825 --> 00:22:11,357
And the User and resource as
well is using the UserModel

387
00:22:11,357 --> 00:22:14,524
where appropriate and that's all fine.

388
00:22:16,059 --> 00:22:18,441
Okay, so I think that's
everything for this video.

389
00:22:18,441 --> 00:22:21,284
And remember, it's really
important to check your code

390
00:22:21,284 --> 00:22:23,475
and read it over and over and over again

391
00:22:23,475 --> 00:22:26,787
and try it with Postman
every time that you make

392
00:22:26,787 --> 00:22:28,597
a few changes.

393
00:22:28,597 --> 00:22:33,347
While developing this
course I literally made tens

394
00:22:33,347 --> 00:22:36,563
of different versions incrementally

395
00:22:36,563 --> 00:22:38,753
and tested each one using Postman

396
00:22:38,753 --> 00:22:41,468
and just to make sure
that everything works

397
00:22:41,468 --> 00:22:44,773
every step of the way and
you should do that as well.

398
00:22:44,773 --> 00:22:45,796
As you're typing your code,

399
00:22:45,796 --> 00:22:47,259
always try it out with Postman,

400
00:22:47,259 --> 00:22:48,814
always look through and read it

401
00:22:48,814 --> 00:22:52,164
and re-read it until you
get so paranoid about making

402
00:22:52,164 --> 00:22:54,468
mistakes that you'll just
spot them immediately

403
00:22:54,468 --> 00:22:58,107
as you make them, but that's
part of software development,

404
00:22:58,107 --> 00:23:00,990
so hopefully you're okay
with signing up for that.

405
00:23:00,990 --> 00:23:02,728
And that's it for this video,

406
00:23:02,728 --> 00:23:05,223
so I'll see you on the very next one.