callWorker

callWorker( process : string , formula : 4D.Function {, param {, ...paramN } : integer } )
callWorker ( process : string , formula : string {, param {, ...paramN } : integer } )
callWorker ( process : integer , formula : 4D.Function {, param {, ...paramN } : integer } )
callWorker ( process : integer , formula : string {, param {, ...paramN } : integer } )

Parameter	Type		Description
process	string | integer	→	Name or number of worker process
formula	4D.Function | string	→	Formula object or Name of project method
param	any	→	Parameter(s) passed to formula/methodName

Description

The callWorker command creates or calls the worker process whose name or ID you passed in process and requests the execution of the code designated by formula in its context with the optional param parameter(s).

The callWorker command encapsulates the param parameters into a message and posts it in the worker's message box.

In the process parameter, you can specify the worker using its process name or its process number:

• If you pass the number of a process that does not exist, or if the process specified was not created by callWorker, callWorker does nothing.
• If you pass the name of a process that does not exist, a new worker process is created.

The worker process is returned by the processInfo command when applied to this process.

In formula, you designate the code to execute in the context of the worker process. You can pass either:

• a formula object. Formula objects can encapsulate any executable expressions, including functions and project methods;
• a string containing the name of a project method. You can pass an empty string; in this case, the worker executes the method that was originally used to start its process, if any (i.e., the startup method of the worker).

You can also pass parameters to formula using one or more optional param parameters. If the formula is a string formula, you must use sequential parameters ($1, $2...). Upon starting execution in the context of the process, the process formula receives the parameter values either in the parameters, or in $1, $2, and so on. In the context of the callWorker command, the following considerations need to be taken into account:

• Standard object or collection type parameters are passed by copy, i.e. Qodly will create a copy of the object or the collection in the destination process if the worker is in a process different from the one calling the callWorker command. In this context, if you want to pass an object or collection parameter by reference, you must use a shared object or collection.

caution

A worker process remains alive until the application is closed or the killWorker command is explicitly called for it. To free up memory, do not forget to call this command once a worker process is no longer needed.

Example

In a Page, a button starts a computation: for example, statistics for the selected year. The button creates or calls a worker process that computes the data while the user can continue to work in the form.

The code called from the button:

var vYear: integer
vYear = 2015 // could have been selected by the user in the form
callWorker("myWorker",formula(workerMethod),vYear)

The code of workerMethod is:

 declare(vYearInteger) //year reference
 var vStatResults : object //to store statistical results
 ... //compute statistics

See also

killWorker
Signal class