Adding a CMS to Your Flask Web App Transcripts
Chapter: Saving content to the DB
Lecture: Tour of existing DB layer
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well, it's time to upgrade our CMS and make all the changes were making permanent
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So far, I've been putting off talking about working at the database because I didn't want to really get it. Was details involved with what we're doing.
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I want to stay really focused on just building the CMS side of things. But now it's time to start saving things beyond just in the memory.
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While our APP is running, much of this application is already built on sequel Alchemy And so what I want to do in this short video is take a quick
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tour of how things are structured already that we can just plug into that overall pattern and framework. First, let's talk about a couple of tables,
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so we have a user table and we're modeling that with a user class. No surprise there with sequel alchemy. We have a shared based class,
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and the way that a class represents a table in our database is that it derives from this class sequel Alchemy Base.
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We change the name of the tables that we wanted to be singular and capital. We wanted to be the little case in users,
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so we set that, and then it has some pretty straightforward stuff. But as an idea, that's a imager,
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its auto incriminating. So we're not to mess with that. You just save something that automatically generates this primary key force.
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Have a name which is notable, given email, which has to be unique. And it hasn't index because it's very common when somebody tries to log in that we
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would say, What's your email? What's your password? Let's go find the user by email, so you want that to be super super quick.
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What else we have a few other things is admin. I guess it's worth mentioning here.
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And obviously, this is the flag that gets set in the database that indicates whether
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or not you are allowed to access the CMS admin section in my default. New users are not admits, as you would expect,
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right, so this is pretty straightforward. One. Let's look it, probably the most complicated thing we've got going on here
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which is the package. It's when you run the site and you look at all the packages. That's what you're seeing.
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So we've got the name of the package being the primary key in this case, and some other staying there stuff like this.
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I guess it gets interesting down here where we have a relationship between the releases for a package and the package itself.
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We also have this cool, multi layer order by so first order by the major version than the minor version than the build version and back.
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Populate the package link on individual releases as you bring him in. So you don't really need to know a whole lot about all of these things were
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not going to do too much with it. But I did want to show you a few things that are in place.
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Also notice that were using type annotations on the columns. And this is overriding what the standard type checker would think.
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Oh, this is a column or their relation, Yes, but at runtime, what it really looks like is a string and a
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list of releases. So we're going to tell Python that's what those are, and that will give us a little bit better helping the editor.
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Right. So there's two exemplar tables or classes models. You also will see this thing called DB session.
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So over here, what we're gonna do is we're going tohave initialization function that gets
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called right at the start up of the APP and what it does is basically, it comes down here, and it checks to see if there is a database file
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specified. And then it's going to create a sequel, light database or open the one that's specified in the file sequelae.
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Right here is the file. Sequelae is really nice because it's already built in the Python. You don't have to install anything.
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It doesn't run as a separate server. Just run your process and it run your Web app in ages, talks to it. That's super cool.
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He probably wouldn't use it for riel Professional Web APS. For those you do something maybe like post GREss or maybe even Mongo DB.
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But for now, it's equal. Light is working great, and we're gonna come over here, set it up and say, create all the tables based on all of the models
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that you have seen, and then it just records. It's initialized, so that's pretty cool. The other thing is, when it's time to talk to the database,
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we have to create a session. So we're gonna go over here and call this function Gonna create session,
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set a little typing to help things get a little bit better because normally the tooling can't figure out what the's session things are.
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Were also allowing you to work with objects after they've been saved to the database. That just makes things easier for us.
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Final thing. We have this different locations where we have to make sure we've loaded all the models before we try to interact with sequel alchemy.
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One clear example is right here before we say create all the tables. It has to be that we've loaded every single model into memory.
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How do you know for sure that you've done that? Maybe pretty clear here, but over in the Olympic world, we also have to do that.
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And that's not really part of this project. It gets a little more tricky.
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So we've got this thing over here where we're just explicitly stating every file we're using every module that has some secret alchemy classes.
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So when we add like a page, we're gonna come over here and have a, you know, pages or whatever we call it,
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and I will make sure that sequel alchemy knows about that class, and that should create tables and start working with it.
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This allows us to just put this in one place and not always think about how we're getting back to it. That's it.
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I guess we could look at one example of using it. Let's go over here to say the user service,
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So it's really quite straightforward. If we want to know how many users are in our database going to create a session and then we go to the session,
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we say We want a query based on this table or this class, this model users We want to just count how many users that are.
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So this is going to return a number, and we always want to explicitly close the session to make sure it's closed up right
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away. And we can do that with a try finally find when we're creating the user. They were to create the user object,
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get the session, had the usual call commit and then close it and then return the user. This part right here is where that expire on commit equals.
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False becomes really, really handy. All right, so using this is not hard,
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but you do want to fit into the existing design patterns and way we've structured stuff with our models and seek welcome and so on.
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So now you know all about it. Hopefully, you like how we put it together.