Re: [Jsbsim-devel] [BUG] Failed to tie property xyz after reset in FlightGear

[Anders G. <and...@gi...>]

On Sun, 17 May 2009, Torsten Dreyer wrote:

> Correct, the error occours only for properties outside the /fdm/jsbsim domain.
> (see my original post). I don't see any reason for not putting them into an
> arbitrary location in the property tree - until it's defined as illegal ;-)
> It currently does not work because of a "design flaw". I don't think it is a
> good idea to have two properties updated for the same purpose - the
> automatically created from the components name and one from the output
> element.

I OTOH find it very reasonable to constrain JSBSim components to 
the /fdm/jsbsim/ subtree. That avoids a lot of potential problems when 
sharing the property tree with an external application (as is the case in 
the JSBSim / FlightGear combination). It also works with the present 
property clean-up scheme.

IIRC the cost of a tied property is very low (as long as it isn't read).

I view touching any property outside /fdm/jsbsim as external 
communication.

> And: <output> properties are not tied, so listeners do not get triggered on
> update.

If my memory serves me right (and a quick test seem to confirm it does) 
it is tied properties that Nasal listeners do not work with. 
So, in fact, it is only if you use <output> you get a property that you 
can listen to, otherwise you don't.

> Jon, just to confirm, properties with relative paths do not produce the error
> message. Your memory still serves you well ;-)
>
> Oh - while typing this, I will try to name a component "../../some/name"
> instead of "/some/name" to check if this works...

IMHO that is a bad idea. But you do as you please, of course.

Cheers,

Anders
-- 
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Anders Gidenstam
WWW: http://www.gidenstam.org/FlightGear/