On Tuesday, October 22, 2013 11:13:22 AM UTC-7, GregD wrote:
> All,
>
> I have a legacy DB that use mnemonics to define state, status and flags of
> several DB objects. I'd like to cache them some way and then have each
> object have methods to return appropriate messages. Most of them are
> defined by a pattern, but not all follow the pattern. Almost all, if not
> all, use the same attributes of status, state and flags. I'd like to use a
> module to do this and then just include the module for the Models that have
> those attributes. However, I don't want to join the table at all and just
> get the cached values.
>
> My thoughts for that module would be to use method_missing and respond_to?
> to create a method that would return the mnemonic message(s) like define a
> method status_message if the model respond_to? :status. This would take
> the instance status integer value into the class's cached status mnemonic
> messages returning the message. My problem is setting up the cache.
>
> Most of the mnemonics follow a specific pattern, like I said, and there is
> a view that returns them all. The pattern is the object name and the
> attribute. Eg. Order would have status, flags, and state attributes and
> have mnemonic type/code/values of "ORDER_STATUSES", "ORDER_FLAGS", and
> "ORDER_STATES" I was thinking of using a class and class level variable to
> store them in a hash. But, I don't like using class level variables for
> numerous reasons. But, I know I would only hit the DB once or limit the
> number of times the DB is called for get those by maybe providing a class
> level method to refresh the hash. The mnemonics are pretty much static
> data, but can be changed (very, very rarely).
>
> Someone has to have done this type of thing before, right?
>
I admit I have a hard time understanding exactly what you want to do. It
would probably be better if you posted examples of your schema and what you
want your model methods to return.
>From what you posted, I'm guessing you want something like:
CACHE = {}
DB[:mnemonics_view].select_hash_groups(:type, [:code, :value]).each do
|key, values|
h = CACHE[key.downcase.to_sym] = {}
values.each do |code, value|
h[code] = value
end
end
Your mnemonic methods would index into this cache:
class Order
def status
CACHE[:order_status][status_column]
end
end
Hopefully that makes sense. If not, you probably need to post an example
of what you want to do.
Thanks,
Jeremy
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