Building Data-Driven Web Apps with Pyramid and SQLAlchemy Transcripts
Chapter: Client and server-side validation
Lecture: Server-side validation
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We're also going to use this over here.
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And this is going to show you another aspect
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of these view models that is beautiful.
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So notice over here that we're saying
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all right, some form data has been submitted to us.
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Right here it's, look at this email
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look at this name, look at this password.
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Well instead of remembering to do this
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and on complicated forms with ten pieces
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like this gets really tiresome really quick.
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We could actually just do like this.
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Even on the Get because state is going to come in
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but it'll just be missing so we could come over
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and say self.requestdict.get('email')
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Or we could just say .email, whichever you feel like.
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That solves those three lines.
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And then this validation, remember I said really
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really there should be three lines.
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You're email is required. You didn't enter it?
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Oh, wait, you entered your email but your name is required.
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You didn't enter it, and so on. Well let's go do that.
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We only want to compute those sorts
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of things on the form POST.
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So let's add another validate function here.
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And when that happens we're going to basically say
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if not self.email self.error equals?
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You must specify an email address.
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And you can imagine, same for name, same for password.
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So over here that is this sort of stuff and remember
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all of these things are already being tracked
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so watch how much simpler this becomes.
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vm.validate, and remember this is totally scalable.
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Like this could become way more involved.
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And it, it means you're more likely
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to write that extra validation code.
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Because it's not making this method even worse
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even harder to understand, right?
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There's, it never gets more complicated than just validate.
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So then you just ask if vm.error
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if there is some kind of error
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were just going to return vm.to_dic().
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Which includes the error.
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Otherwise, we say vm.email
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vm.name, vm.password.
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Done, how sweet is that?
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So, look how clean this method becomes.
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We create our view model and we ask for validation.
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And if there's a problem we just let it exchange
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other data back with potential
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error messages, all sorts of stuff.
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And, otherwise, we carry on.
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Now let's do one more thing, let's go to this part here.
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And let's add, say if self.email.
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Remember we stored this in a simplified form.
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We'll say email == self.email.strip().lower().
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Just to make sure.
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I think we're doing that in the data layer as well
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but let's make sure the data is
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already prepared when it comes in.
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And we can come over here and say things like
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if it's not there we'll just say strip on this as well.
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We're not going to mess with the password.
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They owant their password to be space, they can have it.
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Alright, let's make sure we can still register.
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So over here, we register get, register post.
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Let's see if things are still working.
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Come over here. Right now we're logged in so let's logout.
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And let's register as user, user2.
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At u2.com, get my password.
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Actually, let's first leave some stuff out here.
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Let's leave out the name and the password.
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You must spec, specify your name.
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User2 is my name.
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You must specify password.
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Alright, that's our password.
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Now this should work and we should be logged in as user2.
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Ready, bam, there we go.
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So let's review, we've taken and created
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this RegisterViewModel that has both the ability
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to load the data and then validate it.
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We saw our error handling checking
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to make sure the user name was there
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the actual name was there, the password was there.
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We didn't check email but it's there.
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And then, once all that stuff happens correctly
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we just use the values from it.
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So, what's really beautiful about this is it doesn't
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no matter how much data you exchange, it doesn't
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get more complicated than this.
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The view model is in charge of validating the data
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and exchanging the data with the form.
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You just work with the, the data that's gotten.
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It's real, real nice.
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On this one, they can interact with
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the database as it needs to, all sorts of stuff like that.
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So here, it's going and getting the cookie from the request
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and then it's actually hitting
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the database to populate the user.
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If it doesn't find it, we do some hard
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error handling, we just send them to login.
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Otherwise it passes that onto the view
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which is why we saw that right there, user2.
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So these view models are super, super valuable.
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And we'll be using them for the rest of this course.
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I'm going to go ahead and put view models in place for
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the remaining methods that you don't see.
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Like on packages and so on, but I'm not not going to
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walk you through it because, guess what?
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It's exactly the same as what we've
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been doing in the last two.
