Event Handlers
68
NetLinx Programming Language Reference Guide
If the event handler is specified using an array for DEV, INTEGER, or a DEVCHAN array, GET_LAST
can determine which index in the array caused the event to run.
Event Parameters
It has already been stated that DEFINE_EVENT handlers are stored in an event table providing quick
access to code that must be executed when an event is received. The event table keeps a list of all events
in a sorted order to more quickly determine which code needs to be accessed for a giving incoming
event. The event table is built before
DEFINE_START runs and it not changed anytime after that. As a
result, there are certain rules that must be applied to the parameters used in
DEFINE_EVENTs.
Since the event table is built before
DEFINE_START, all event parameters must contain the correct
information prior to
DEFINE_START. This requires that all EVENT parameters must be defined at
compile time. In addition, many parameter "shortcuts" to help fulfill this requirement.
Using
BUTTON_EVENT as an example, the simplest version of event parameters is a device and channel
reference. In the following example:
Example 1:
DEFINE_DEVICE
dvTp = 128:1:0
DEFINE_EVENT
BUTTON_EVENT[dvTp,1]
{
PUSH:
Send_String 0,'Button 1 of dvTp was pushed'
}
The device, dvTp, was defined in the DEFINE_DEVICE section, which has the effect of making it an
initialized variable of type
DEV, and the channel number was a hard-coded value of 1. Since both of
these value were defined at compile time, the event is entered into the event table correctly. Let's take
another example:
Example 2:
DEFINE_DEVICE
dvTp = 128:1:0
DEFINE_VARIABLE
Integer nMyChannel
DEFINE_START
nMyChannel = 1
DEFINE_EVENT
BUTTON_EVENT[dvTp,nMyChannel]
{
PUSH:
Send_String 0,"'Button ',ITOA(nMyChannel),' of dvTp was pushed'"
}
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