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  • WLanguage procedure
  • Special cases
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Stored procedures
<Source>.Track (Function)
In french: <Source>.Surveille
HFSQL Client/ServerAvailable only with this kind of connection
Starts tracking the write actions (addition, modification or deletion) performed on a file found on a HFSQL server. In case of modification, a specific procedure can be triggered.
This track can be stopped by <Source>.TrackStop.
// Starts tracking the Order file
// The ProcessOrder procedure is called whenever a record is added to the data file
Order.Track(ProcessOrder, hRecNumAll, hsAdd)
<Result> = <Source>.Track(<WLanguage procedure> [, <Record number> [, <Action to track>]])
<Result>: Boolean
  • True if the tracking is enabled,
  • False otherwise. To find out the error details, use ErrorInfo.
<Source>: Type corresponding to the specified source
Name of HFSQL data file to use. The data file is associated with a connection and with a server.
<WLanguage procedure>: Procedure name
Name of WLanguage procedure ("callback" procedure) that will be called when a change is detected in the specified data file. This procedure has the following format:
PROCEDURE <Procedure name>(<Name of modified file>,
<Modified record number>, <Action>)

  • <Name of modified file> is a data source corresponding to the modified HFSQL data file,
  • <Modified record number> corresponds to the number of the modified record (equivalent to the number returned by <Source>.RecNum),
  • <Action> corresponds to the action that triggered the procedure. The possible values are:
    hsAddProcedure started once a record is added into the data file.
    hsModificationProcedure started once a record is modified in the data file.
    hsCrossProcedure started once a record is crossed in the data file.
    hsDeletionProcedure started once a record is deleted from the data file.
<Record number>: Optional integer
  • Number of the record to track.
  • hRecNumAll constant to track all the records found in the data file (which means the entire data file).
<Action to track>: Optional constant (or combination of constants)
Actions to track for which the procedure will be started:
hsAddMonitors the operations for adding records.
hsModificationMonitors the operations for modifying records.
hsCrossMonitors the operations for crossing records.
hsDeletionMonitors the operations for deleting records.

WLanguage procedure

The WLanguage procedure is called in the main thread of the application, with the HFSQL context corresponding to the procedure:
  • If the procedure is a local procedure of a window that is using an independent context, the context used will be the one of the window.
  • If the procedure belongs to a component that is using an independent context, the context used will be the one of the component.
The procedure associated with <Source>.Track can be called at any time in the application.
If the procedure performs HFSQL browses or moves in the data files, this will impact the application (like the timers).
Therefore, you may have to call <HFSQL File>.SavePosition and HRestorePosition to save the contexts of files used.
Multitask must not be used in the procedure code.

Special cases

The track is defined for a data file and a connection:
  • If the physical name or the connection associated with the logical file name changes, the file tracked by the server remains the one specified during the call to <Source>.Track.
  • If the connection is closed, the track is automatically stopped.
  • The tracking continues if the connection is lost then restored by automatic reconnection.
To stop tracking the data file, use <Source>.TrackStop.
Versions 24 and later
<Source>.Track and <Source>.TrackStop can be used in a Windows service.
New in version 24
<Source>.Track and <Source>.TrackStop can be used in a Windows service.
<Source>.Track and <Source>.TrackStop can be used in a Windows service.
Component : wd250hf.dll
Minimum version required
  • Version 25
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