RESTful and HTTP APIs in Pyramid Transcripts
Chapter: Conclusion
Lecture: Lightning review: View models

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0:01 After content negotiation and the different renderers
0:03 we added validation to our api which was sorely missing up until this point,
0:07 but once we did, the actual validation code simply overwhelmed the api code
0:13 and the important code if you will, by just totally filling up
0:16 so we said let's create this abstraction called a view model
0:19 whose job is to do the validation, to do the transformation
0:22 from original object into rich Python objects and so on.
0:25 So here, after having a super bloated update auto method,
0:29 we condensed it back down, so we're doing the standard web stuff in gray
0:33 so we're getting the request.json_body and we have to do that in the api method
0:37 because there's not really a good way to do that without passing the request itself
0:41 so we just go ahead and say fine we'll have to do this here, a little bit of web work
0:44 and then we create our view model, we give it the initial data,
0:47 call compute details and then it populates its errors response
0:52 which is a list of problems that may have encountered
0:54 and if it has one, it just says hey there's some kind of problem
0:57 like 400 bad response, 404 missing, 403 permission denied, whatever
1:01 and it sends the error text and the status back.
1:04 All right so that orange line or red line section in the middle
1:08 no matter how much validation we add it's going to stay that simple
1:11 and if we want to test the validation,
1:14 we don't need to do that by mocking of the web request in the database
1:17 we just give it this object and we can test that on its own.
1:20 If we make it through that, then we're really down
1:22 to what we wanted to do in the first place,
1:25 take a car, update the database and either say that worked or it didn't.
1:27 So here we're returning the error 400,
1:30 because the repository was doing some validation as well
1:33 but it could also be 500, we need to be more careful
1:39 about the exception type that we're catching
1:41 so like a database exception probably our fault,
1:44 like couldn't connect, some sort of other validation exception,
1:47 well maybe we do 400 here.