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	✓