Building Data-Driven Web Apps with Pyramid and SQLAlchemy Transcripts
Chapter: Client and server-side validation
Lecture: Viewmodel validation
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Saw the one job of these view models
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and that's to do the data exchange.
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The other is validation.
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So, let's look at that now.
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Here we have our gathering of data, right.
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We're creating this view model based on a request
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and it's populating even normalizing some of our data
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like first name, last name, and email.
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Great but on the POST side of things
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where we're taking this data in
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and we're doing a operation based on
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assuming that we have good data
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like that they actually set the name
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they set the email and so on.
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We want to do validation.
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So that's where this error thing comes in.
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So we're going to do this validate
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and we're going to say check the first name or last name
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and if either of them are empty
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we'll say you must specify your full name.
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If there's no email you must specify an email address.
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If you don't specify a password similarly
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you get a message that says that.
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So, we set these errors and then the
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action method or the view method
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its job will be to make sure that there's no errors
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before it actually does its operation.
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We can even do things that interact with the database.
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So, here this is a registration operation.
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We did basic validation on the form values.
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First name, last name exist and are not empty.
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Email is set, we could do regular expression
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to say this is a valid email
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or something simpler like check for @ and.
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A few things like that.
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But here we're actually going alright
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once you pass all the basic validation
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let's go to the database and see if there
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is a user with the email address
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that you're trying to register as
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because if there is we're not going to let you do that.
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The user already exists, right.
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So, we have these sort of basic validation
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and higher level validation we can do.
