Building data-driven web apps with Flask and SQLAlchemy Transcripts
Chapter: Course conclusion
Lecture: viewmodels
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When we were accepting user input
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we saw that there's a lot of validation
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a lot of data exchange
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and other things we have to do.
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And that's not so much fun.
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And the exact data and the format
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of the data that we want to pass back and forth
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also takes a lot of work.
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So we decided to apply this design pattern
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called view models.
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And the idea is the view models
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are tightly tied to the HTML form that
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they're exchanging data with.
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They know how to get the data
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from the form and provide it back to it
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or things like drop downs and where it needs it
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and roundtrip it and so on.
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It also knows how to do all the validation.
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And that can be basic validation like
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Hey, we require that you type in an email
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address here, or, This has to be a number,
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or, It has to bigger than five, and so on.
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But it can also be richer, deeper validation like
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Sorry, you can't register here.
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You can't create an account with that email
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'cause that email address is already
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tied to another user.
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Maybe you should just try to login
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and reset your password.
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And it's both made testing easier
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'cause we can test the view models directly
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and just do validation there.
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Don't have to involve Flask
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and HTTP infrastructure, and so on.
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It also made our action methods
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and our view methods much simpler, right?
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They don't get larger and more complex
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as we add more validation.
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Just the one place where validation goes
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the view models, does. But that's okay.
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That's its job. Strongly recommend this pattern.
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There's some other add-on libraries
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for Flask and stuff that you can use for forms and whatnot.
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But I really like this pattern
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because you have complete control over it
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and it's super straightforward and good for testing.
