On Thursday, March 26, 2015 at 8:19:28 PM UTC+11, Colin Yates wrote:
> First - loving re-frame, mainly because it names the abstractions I found
> myself fudging around with when using om (which is also great).
>
> Anyway, in om I attached a watcher to the root app-db which validated against
> a global schema, and whilst it stopped invalid data getting *into* the atom
> (as opposed to the 'after' middleware) it sucked at reporting errors. I am
> not clear on the best approach using re-frame.
>
> My app is non-trivial and has a number of discrete logical 'pages', none of
> which care about the others, so it makes sense to do something like:
>
> {:page-a {...}
> :page-b {...}}
>
> In a given page there might be quite a deep tree as well, and each handler
> tends to be quite focused (using (path ...)) on a sub-tree.
>
> I could:
> - continue with the watcher on the ratom
> - have a macro which defines a handler with just its schema (which would be
> _very_ noisy)
> - attach the validation at the 'page' level
>
> My preference is by far at the 'page' level, but I am struggling to see the
> plumbing. I would be happy if each handler validated the 'page' structure,
> but because the handlers typically use the path they don't have access to the
> higher level page.
>
> In addition, I can't assume data-symmetry between the db and the schema (e.g.
> I can't simply take the 'path' provided to (path..) and (s/validate (get-in
> big-schema 'path')) as the schema uses predicate functions (s/both etc.).
>
> I hope that is clear - any suggestions?
>
> Thanks!
First, if you haven't seen it already, I'll recommend reading this:
https://github.com/Day8/re-frame/wiki/Debugging-Event-Handlers
So, don't do schema checks via a watcher -- the re-frame way is to use
middleware.
Next, if you have largely independent "pages", treat them as almost independent
sibling apps. Each page has its own source sub-directory containing associated
handlers.cljs, subs.cljs, views.cljs and, importantly for this discussion, its
own db.cljs schema.
Each page gets its own "branch" of "app-db". And in each page's db.cljs there
should be a schema for that branch.
All the handlers for one page should use "path" middleware to "focus" the
page's handlers to that page's branch of "app-db". Equally, each handler for
that page should have middleware which checks that page's schema after each
handler has run. (This does mean your schema-checking middleware has to be put
to the LEFT of the path middleware
https://github.com/Day8/re-frame/wiki/Using-Handler-Middleware#6-ordering)
Does that make sense? I can further clarify if necessary.
--
Mike
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