I have a model class, let’s say it’s a Book. I need it to be displayed on the screen. I want to have an escaped version of it, so I do not need to escape fields manually.
What should I do? I can
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add a wrapper over the
Bookthat returns escaped values (e.g.EscapedBook); but every time when I change the book, i need to change the wrapper – at least to add/remove methods. -
run the model through some AOP and generate proxy before it is going to be displayed on the screen.
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or run the model through some util that is going to escape all string properties.
IMHO this is not quite a business behavior, so I would like to keep this on the UI layer.
A wrapper is the right way to go here — you really want the UI part of the UI layer to just reflect what is given and not be responsible for more than very technical bits of filtering content. I would run with the first option you are looking at and create a specific subclass for the UI layer to handle this task.
The real cost from a writing code perspective isn’t having to update your EscapedBook whenever the underlying class changes — underlying classes changing is going to change a lot of things down the logical line. You’d be better off having the internal representation talking to a single class rather than speaking directly to a dozen different things in the front end application.
This front-end specific class could very well be generated via a proxy or AOP process — that is really a tactical decision depending on what the stack is and what other dependencies you have. You might mean having a straight-through dedicated proxy rather than a separate class. This isn’t a horrible idea on the surface but I would prefer the dedciated class concept in the end — it is more flexible to separate the problems in the end.
The utility class is best avoided here — you will end up with things like ContentUtil.CleanPage(book.Pages[1]) all over the UI layer and that will hurt to fix when you re-think things. Globals are bad, even when globals are stateless utility functions.
One thing I would not throw out is having this be generated in the business layer — generating properly escaped content is a testable business requirement of the application I’d rather test against the business layer versus trying to write automated tests of the UI.
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