New signal
New signal { ( description : Text ) } : 4D.Signal
Parameter | Type | Description | |
---|---|---|---|
description | Text | → | Description for the signal |
Function result | 4D.Signal | ← | Native object encapsulating the signal |
History
Release | Changes |
---|---|
17 R4 | Added |
Description
The New signal
command creates a 4D.Signal
object.
A signal is a shared object which can be passed as parameter from a worker or process to another worker or process, so that:
- the called worker/process can update the signal object after specific processing has completed
- the calling worker/process can stop its execution and wait until the signal is updated, without consuming any CPU resources.
Optionally, in the description parameter you can pass a custom text describing the signal. This text can also be defined after signal creation.
Since the signal object is a shared object, it can also be used to maintain user properties, including the .description
property, by calling the Use...End use
structure.
Returned value
A new 4D.Signal
object.
Example
Here is a typical example of a worker that sets a signal:
var $signal : 4D.Signal
$signal:=New signal("This is my first signal")
CALL WORKER("myworker";"doSomething";$signal)
$signaled:=$signal.wait(1) //wait for 1 second max
If($signaled)
ALERT("myworker finished the work. Result: "+$signal.myresult)
Else
ALERT("myworker has not finished in less than 1s")
End if
The doSomething method could be like:
#DECLARE ($signal : 4D.Signal)
//any processing
//...
Use($signal)
$signal.myresult:=$processingResult //return the result
End use
$signal.trigger() // The work is finished
Properties
Command number | 1641 |
Thread safe | ✓ |