Yes, now that I've had a little time to think about this I can see numerous
advantages. For instance the function does not need to be type aware - and
new layers could be added in the future and not require code changes. Just
took me a while to get my head around it. Thanks.
On Fri, Jul 12, 2013 at 10:24 AM, jody.garnett [via OSGeo.org] <
[email protected]> wrote:
> Please consider the functions as .. FUNCTIONS :) ie only calculate a value
> based on their input parameters.
>
> It helps if you think of them not being specific to one kind of feature.
>
> --
> Jody Garnett
>
> On 12/07/2013, at 10:51 PM, lindsey <[hidden
> email]<http://user/SendEmail.jtp?type=node&node=5066092&i=0>>
> wrote:
>
> > OK that makes more sense. Thanks for the reply. So it sounds like my
> > understanding of the theory was ok, but my implementation was bad. I
> guess
> > it's time to look at a little code. For the function that I'm working
> on, I
> > send in the following ogc:Filter xml in my query request via WFS:
> >
> > <ogc:PropertyIsEqualTo matchCase="true">
> > <ogc:Function name="TrajectoryQuery">
> >
> <ogc:Literal>-111.97777222222223,40.78838888888889
> > -75.24086666666666,39.87225</ogc:Literal>
> > <ogc:Literal>25000.0</ogc:Literal>
> > <ogc:Literal>1343857109000</ogc:Literal>
> > <ogc:Literal>300.0</ogc:Literal>
> > </ogc:Function>
> > <ogc:Literal>true</ogc:Literal>
> > </ogc:PropertyIsEqualTo>
> >
> > I recognize that the first argument should probably be a geometry type
> > instead of a literal, but I'm taking it one step at a time and figured
> this
> > would be easier to start with. So the idea is that the function would
> use
> > these parameters to perform some calculations on the records from the
> data
> > store to decide whether or not they meet some criteria that must be met
> in
> > order to be rendered on the WFS client.
> >
> > Here is how I set up those parameters in my FunctionImpl subclass:
> >
> > public static final FunctionName NAME = new FunctionNameImpl(
> > "TrajectoryQuery", Boolean.class,
> > parameter("geometry", String.class),
> > parameter("width", Double.class),
> > parameter("queryTime", Long.class),
> > parameter("speed", Double.class)
> > );
> >
> > For our current purposes, the evaluate method could be as simple as
> this:
> >
> > public Object evaluate(Object feature) {
> > System.out.println("FEATURE=" + feature);
> > return (feature != null);
> > }
> >
> > It is worth noting however that if I add lines to do things like this:
> >
> > double width =
> > super.getParameters().get(1).evaluate(feature,Double.class);
> >
> > ... then all the proper values are there. So it does receive the
> parameters
> > that I pass in.
> >
> > So in other words, my code does meet the criteria that you mention would
> be
> > problematic (all literals). So it sounds like there may be a couple
> ways to
> > address this:
> >
> > 1 - Perhaps making the first arg an actual geometry is better, but not
> sure
> > how that would be associated with a property on the data store feature
> > (though it does have a geom field).
> >
> > 2 - Perhaps I can directly reference other properties of the feature in
> the
> > args... I'll do some more review of the docs.
> >
> > I'll research these items while awaiting more feedback, but if you have
> any
> > other tips that might help me get just that feature != null check
> working
> > then I'd be very grateful.
> >
> > Thanks.
> >
> >
> >
> >
> >
> >
> >
> > --
> > View this message in context:
> http://osgeo-org.1560.x6.nabble.com/Re-Geotools-devel-Custom-Filter-Function-Getting-Started-Question-tp5065918p5066045.html
> > Sent from the geotools-gt2-users mailing list archive at Nabble.com.
> >
> >
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