[PEAK] External connectors now in Trellis SVN
Phillip J. Eby
pje at telecommunity.com
Thu Mar 20 15:25:46 EDT 2008
An experimental version of the Sensor and Effector cell classes is
now available in Trellis SVN. There are no docs besides the
docstrings, and relatively few tests, but they appear to work correctly now.
The simplest way to create an external connection cell is to pass a
trellis.Connector() as the "rule" of a cell. For example:
someattr = trellis.rule(
Where readfunc is a 0-argument callable returning a value from the
external system, connect is a 1-argument callable taking a Sensor
whose .receive() method should be called with a value whenever the
external system value changes, and disconnect is a 1-argument
callable that will take the return value of connect() and stop
issuing callbacks to the sensor's .receive() method.
This doesn't support write-backs to the external system; you can
manually create a "Cell(..., writer=writefunc)", however, and
writefunc() will be called whenever the cell value is changed by
*setting* it (as opposed to recalculating it). Currently, the
writefunc is called during the "observer" (soon to be called
"performer") transaction phase, meaning it can't change other trellis
data (because of course, it's intended to write to external systems).
All this stuff is experimental at this point, meaning the APIs might
change. Feedback is welcome!
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