Building data-driven web apps with Flask and SQLAlchemy Transcripts
Chapter: Introducing the Flask framework
Lecture: Building block: Views

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0:00 Here's a view method
0:01 and we're actually going to start by
0:03 getting a hold of this thing called an app.
0:06 It's almost always named an app
0:07 you can name it whatever you want it.
0:08 It's a variable, but we're going to create
0:10 an instance of our Flask app like this
0:12 and this is a singleton so it gets pretty interesting
0:15 sharing this across files
0:16 and we'll talk about some cool patterns for doing that.
0:18 We get this single instance of an app
0:21 and we're going to go and write a view method
0:24 and put a decorator on there.
0:26 So we going to add the app.route decorator.
0:28 This is going to be a route, talk more about that in a second
0:31 but notice it defines a category
0:33 and the category's actually passed in
0:35 but if there's no data from the route
0:36 this is just a void method.
0:38 There's no parameter's or anything like that.
0:41 We're going to write this function that accepts any
0:42 arguments from the route, and nothing else really
0:45 and then in here we're going to do all of our logic.
0:48 We're going to look at the URL, what this method represents
0:50 the logged in user, things like that and make a decision.
0:54 Here we're doing something very simple.
0:55 We're just saying, there's not a lot to show
0:57 we're just going to render out the category static HTML
1:02 and we need to pass one thing to it
1:04 and the name of the thing we're being passed is called key
1:07 and the value of it is just value
1:10 something like that, okay.
1:11 So, somewhere in the category template
1:13 it's going to look at that potentially
1:15 and, you know, show that somehow in the HTML
1:18 and we're just going to return that back to Flask
1:21 and then we'll render that as a response to the user.
1:24 So here we're going to take these values and pass them over to
1:27 this template called category dot HTML.
1:31 Now that was cute, but not very realistic.
1:33 Let's take something a little more realistic here.
1:36 So we're going to say, here is the method that receives
1:39 the post request for registering with account.
1:43 So that means that there's an HTML page
1:45 there's a whole bunch of details like
1:46 what's your name, what's your email and so on
1:48 and there's a button that says register.
1:50 When they click it, it's going to run this.
1:53 So there's more stuff happening here.
1:54 So we're going to come in and first collect all of the data
1:57 that's been submitted to us from Flask.
2:00 Here we're saying, go to the form and get the email value
2:02 and the password value, but there could be other data
2:05 some from the URL, some from cookies, all sorts of stuff.
2:08 Want to collect the data
2:09 and then we're going to do some sort of validation.
2:12 We're going to check
2:13 and see if we can create a user based on that
2:15 and maybe we can because there's already an email used
2:18 right, there's already an account existing
2:20 or something like that. If there is none
2:22 and there's no ability to create this account
2:24 that's probably some kind of error.
2:26 So we're going to return a render template.
2:29 The same template, probably given before and say
2:31 There's an error, can't create your account for
2:33 reasons x, y and z," but if that worked
2:35 then we're going to do something else
2:36 like we're going to show them a message that says
2:40 Welcome to our community, or more likely we'll redirect
2:43 them over to their account page, or some other view.
2:45 Right, so this is more like what it looks like.
2:48 Right, we've got a function
2:50 we get the data from forms or other locations
2:53 do some processing, and then we either handle the error
2:57 or we handle the proper happy path.