Avantec,
That's actually an interesting question and you need a little knowledge of (1)
How actual global variables work in Ruby, and (2) how the Rails boot process
works, and (3) How A-Rels (ActiveRelation objects) work under the hood.
Typically what you are trying to do is not actually done. That's because data
in the database changes, so 98% of the time you want the query to re-fire when
it goes to look something up. To achieve that (not what you asked for), you
typically use a scope on the model.
Caching the result is the next step-up from re-firing each time. That is often
done with a memorized method, something like this:
class User
def self.all_admin_users
@all_admin_users ||= self.where(role: 'admin')
end
end
But note that even global variables are garbage collected when the current
process ends (which in a web scenario is when the response is finished). So
that will re-fire on the next web request.
If you truly want to load this in an initializer and have it persist across web
requests, then you would indeed do that in an initializer during when the Rails
app boots up. But that is rarely useful, since in order to make changes to that
data you would have actually restart the entire web process. Generally it's
better just to optimize the query, have it be a memorized method, and let it
re-fire on each web request.
-Jason
On Oct 22, 2014, at 2:18 AM, Avantec Van <[email protected]> wrote:
> Hi,
> I've code like this
>
> x_data = Model.where(column: 'xyz')
>
> and I wanted to use 'x_data' everywhere like models, controllers,
> helpers, etc.
>
> I used in this way
>
> module Global
> X_DATA = Model.where(column: 'xyz')
> end
>
> but when using Global::X_DATA it is firing query every time.
>
> Where should I write this to use it everywhere and query should not be
> fired more than once.
>
> add this in initializers is a good practice?
>
> Please help.
>
> Thanks in advance.
> Avantec
>
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----
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[email protected]
http://www.jasonfleetwoodboldt.com/writing
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