Re: [Geotools-devel] How to use "anonymous" OGC Filter Functions

[Michael B. <mic...@gm...>]

I'm out of my depth here, but wouldn't a new marker
UnsimplifiableFunction interface, of which the VolatileFunction
interface could be a descendant, lead to a much simpler and more
understandable system now and in the long term ?

Michael

On 9 July 2012 14:02, Jody Garnett <jod...@gm...> wrote:
> This works ok except when it comes to use SimplifyingFilterVisitor
> down in the call chain (an hence any DuplicatingFilterVisitor
> specialization), because visit(Function) will try to return a new
> instance looking up the function factory by name, which does not
> exist.
>
> Can you detect this case, and "reuse" the original function with warning?
>
> For this reason, and in order to keep it as simple as possible, I
> wonder if it would be ok to say that VolatileFunctions are not
> "cloneable", and so instruct DuplicatingFilterVisitor.visit(Function,
> Object) not to go through the SPI lookup for VolatileFunctions, but
> return them directly.
>
> I have a hesitation there as that is not quite the meaning of
> VolatileFunction we were going for; but I see how it can work.
>
> I will note, that if you cannot make a copy, then any simplifications made
> on the parameters to your function cannot be accepted.
>
> Another possibility is to add a separate marker interface, but I would
> rather avoid bloating the API.
>
> See if you can detect the failure; and use a warning (avoids the API bloat
> without introducing a marker interface).
>
> 1) Suggestion not just a marker interface but something that lets you
> duplicate:
>
> interface class InternalFunction extends Function {
>    InternalFunction duplicate( Expression... params);
> }
>
> 2) Special case DuplicatingFilterVisitor - i.e. check for the marker
> interface "Clonable" and a public "clone" method you can call via reflection
>
> Jody
>
>
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