Moving us along the road to supporting better thread- and process- separation
of the simulator elements, I've added a first attempt at at 'propertyObject'.
This is a template wrapper for SGPropertyNode*, with conversion operators
to/from the related primitive type.
I.e:
simgear::PropertyObject<int> frameRate("/sim/rendering/fps");
int theFrameRate = frameRate; // maps to getIntValue
frameRate = 1234; // maps to setIntValue
if (frameRate == 789) {
...
}
and so on. (The std::string variant tries to convert nicely to char*
too, where possible)
To the extent possible by C++, once you've declared a property object, you
should be able to treat it exactly like a plain int/double/bool/string, but of
course the actual storage is the property. (if you find areas where this falls
down, of course let me know, or fix them)
The goal of the PropertyObject is that it's hard to use inefficiently - it
lazily does the the property lookup, but caches the result.
It has another interesting feature, suggested by ThorstenB - if you try to read
an invalid path, it doesn't silently succeed - it throws an exception! This is
to avoid lurking typos in property paths, which has been an issue. (I will be
adding a 'weak' variant, that takes a default value, for the cases where people
want to read a property that might not exist)
Suggestions are most welcome - for example there's no read-only version at the
moment, but there could be.
Apart from being a nicely short syntax, there is another goal - tied properties
are a menace, for thread-safety, for un-tie-ing cleanly on subsystem shutdown,
and for not firing change listeners. My hope here is to create something that
has semantics that work in a multi-threaed or multi-process world - but which
is as painless to use in code as a tied value. I think I've succeeded, but time
will tell.
(One other thing I will be adding, probably to SGPropertyNode itself, is a
nicer listener syntax, since I'm aware of various pieces of code that use tied
setters as a value-changed notification - SGPropertyChangeListener is a rather
cumbersome solution for this)
I'm not going to start converting tied properties to use propertyObjects next
week, or next month, but certainly next year. The hope is that by that time,
this code is mature, efficient and so on - so please try it, use it and fix it!
Regards,
James
------------------------------------------------------------------------------
Beautiful is writing same markup. Internet Explorer 9 supports
standards for HTML5, CSS3, SVG 1.1, ECMAScript5, and DOM L2 & L3.
Spend less time writing and rewriting code and more time creating great
experiences on the web. Be a part of the beta today
http://p.sf.net/sfu/msIE9-sfdev2dev
_______________________________________________
Flightgear-devel mailing list
Flightgear-devel@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/flightgear-devel
