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