Building Data-Driven Web Apps with Flask and SQLAlchemy Transcripts
Chapter: Client and server-side validation
Lecture: Using a viewmodel
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Now with this view model base in place
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let's go and actually see how we might use it.
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This is what is actually calling for
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the view model idea the most.
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But let's start with something simpler.
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Just this index, like all we want to do
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is simply show the user details on the screen.
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So we've got to get the user_id
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and potentially, the user as well.
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So, let's go over here to the account
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and we'll have a index view model, something like that.
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We could call it AccountIndexViewModel
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but I'll leave it up to you how you want to name these.
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And it turns out to be really straightforward, what we need.
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We'll come over here and say IndexViewModel.
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And it's going to derive from ViewModelBase.
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So let's import that.
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And actually, I'd like to name it slightly differently.
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Something like that, so it doesn't conflict
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with our class name which what we actually care about.
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So we're going to have another initializer here
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and it's not actually going to take any arguments
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'cause we're not getting any arguments here
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or anything like this.
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So we're going to come down there
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and the first thing we have to do is
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PyCharm miscellaneous
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add a call to super so it'll write this
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or we could write it ourselves.
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And then, let's look at what we're exchanging.
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Well, this part right here we
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have to get an exchange for that
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and that's actually happening already.
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We also have to go over and get the user.
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So let's try that.
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We'll come over here to our IndexViewModel
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and well say self.user is user_service
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got to import that.
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What do we pass here?
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Remember the base class is already setting that up
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and that happened already there
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so we'll say self.user_id, super!
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And this may or may not come through
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Now what else do we have to do?
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Let's actually go back and find out.
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So we're going to go over here and create a vm
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which is a IndexViewModel, like so.
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Create one of these.
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Now this already happens, and so does this.
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So all we have to do is go down here
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and say vm.user and let's go ahead
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and check that actually the query went down to the database
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and found a real user, 'cause maybe somehow
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they deleted their account or whatever.
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All right, if we can't actually get a user
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from the database they have to go login.
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Look how that got simpler, that's nice.
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Now remember, over here we had to do this as well.
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Now what do we return?
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All the fields and stuff contained within this view model.
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There is this extra error thing
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but it doesn't matter, we're just going to not use it
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and we'll just say to_dict, and that's it!
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Look how much cleaner this is become.
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And as we add more information to be exchanged
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this part here gets no more complicated.
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It's this data exchange bit, and this is pretty simple
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but we're going to get more interesting stuff
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as we move down the line here in this file.
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But already this has gotten better.
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Well, I say it gets better, it's actually going to be better
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if it really continue to work but have a better style serve.
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All right, it looks like it restarted.
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Let's go and see that it still works.
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All right we're still logged in, ta-da!
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There we go, so we got up here, the user_id info
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we got here, the actual user object
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and then we pass some other information
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that we technically don't need.
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Cool, huh?
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So here's a simple version of using a view model.
