On Monday, April 28, 2014 8:34:46 PM UTC-7, russ m wrote:
>
> Hi All,
>
> Is there any good way to hook a model such that the hook function is run
> *before* a select query is issued to the database?
>
> My use case is a database that is caching resources from a crappy REST
> source that only supports "get resource by ID" and "get all resources
> modified since this timestamp" operations. At the moment the cache is
> updated on a schedule (so is always a little stale, and is read-only to our
> application), and I'd like to try out refreshing the cache on every
> retrieval of a Sequel::Model object.
>
If you are refreshing the cache on every retrieval, then you probably
should not be caching at all.
> As far as I can tell I can't use the Sequel::Model#initialize like the
> AfterInitialize
> plugin does, since model objects aren't instantiated unless the dataset
> query returns rows.
>
> Before I wade into datasets to see where/how to hook them, can anybody
> point me at a good spot to look at doing this?
>
The only place I can think of to do this is to override Dataset#each for
the model's dataset:
ModelClass.dataset_module{def each; refresh_cache; super end}
But that may refresh the cache more often than you want. A better approach
if this is a web application is to add a before hook or rack middleware
that will reload the cache before the appropriate actions. That way you
are only refreshing once per web request.
Thanks,
Jeremy
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