Building data-driven web apps with Flask and SQLAlchemy Transcripts
Chapter: Introducing the Flask framework
Lecture: Building block: Views
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Here's a view method
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and we're actually going to start by
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getting a hold of this thing called an app.
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It's almost always named an app
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you can name it whatever you want it.
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It's a variable, but we're going to create
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an instance of our Flask app like this
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and this is a singleton so it gets pretty interesting
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sharing this across files
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and we'll talk about some cool patterns for doing that.
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We get this single instance of an app
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and we're going to go and write a view method
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and put a decorator on there.
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So we going to add the app.route decorator.
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This is going to be a route, talk more about that in a second
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but notice it defines a category
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and the category's actually passed in
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but if there's no data from the route
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this is just a void method.
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There's no parameter's or anything like that.
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We're going to write this function that accepts any
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arguments from the route, and nothing else really
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and then in here we're going to do all of our logic.
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We're going to look at the URL, what this method represents
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the logged in user, things like that and make a decision.
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Here we're doing something very simple.
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We're just saying, there's not a lot to show
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we're just going to render out the category static HTML
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and we need to pass one thing to it
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and the name of the thing we're being passed is called key
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and the value of it is just value
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something like that, okay.
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So, somewhere in the category template
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it's going to look at that potentially
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and, you know, show that somehow in the HTML
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and we're just going to return that back to Flask
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and then we'll render that as a response to the user.
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So here we're going to take these values and pass them over to
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this template called category dot HTML.
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Now that was cute, but not very realistic.
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Let's take something a little more realistic here.
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So we're going to say, here is the method that receives
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the post request for registering with account.
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So that means that there's an HTML page
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there's a whole bunch of details like
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what's your name, what's your email and so on
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and there's a button that says register.
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When they click it, it's going to run this.
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So there's more stuff happening here.
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So we're going to come in and first collect all of the data
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that's been submitted to us from Flask.
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Here we're saying, go to the form and get the email value
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and the password value, but there could be other data
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some from the URL, some from cookies, all sorts of stuff.
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Want to collect the data
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and then we're going to do some sort of validation.
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We're going to check
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and see if we can create a user based on that
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and maybe we can because there's already an email used
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right, there's already an account existing
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or something like that. If there is none
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and there's no ability to create this account
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that's probably some kind of error.
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So we're going to return a render template.
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The same template, probably given before and say
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There's an error, can't create your account for
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reasons x, y and z," but if that worked
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then we're going to do something else
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like we're going to show them a message that says
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Welcome to our community, or more likely we'll redirect
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them over to their account page, or some other view.
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Right, so this is more like what it looks like.
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Right, we've got a function
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we get the data from forms or other locations
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do some processing, and then we either handle the error
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or we handle the proper happy path.
