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- WLanguage procedure executed in the main thread
- WLanguage procedure executed in a secondary thread
- Special cases
<Fuente>.Track (Función)
 Disponible solo con este tipo de conexión
Starts watching write actions (add, modify or delete) performed on a file in an HFSQL server. In case of modification, a specific procedure can be triggered.
Commande.Surveille(TraiteCommande, hRecNumAll, hsAdd)
Sintaxis
<Result> = <Source>.Watch(<WLanguage procedure> [, <Record number> [, <Action to watch> [, <Runtime mode>]]])
<Result>: Booleano - True if the data file watch mechanism is enabled,
- False otherwise. To get more details on the error, use ErrorInfo.
<Source>: Tipo de fuente especificada Name of HFSQL data file to use. The data file is associated with a connection and with a server. <WLanguage procedure>: Nombre del procedimiento Name of the WLanguage procedure ("callback") called when a change is made in the specified data file.
For more details on this procedure, see Parameters of the procedure used by <Fuente>.Track. <Record number>: Entero opcional - Number of the record to watch.
- hRecNumAll constant to watch all the records in the data file.
<Action to watch>: Constante o combinación de constantes opcional Actions to watch for which the procedure will be started: | | | hsAdd | Monitors the operations for adding records. | | hsCross | Monitors the operations for crossing records. | | hsDeletion | Monitors the operations for deleting records. | | hsModification | Monitors the operations for modifying records. |
<Runtime mode>: Constante opcional WLanguage procedure execution mode:
| | | hSecondaryThread | Execute the WLanguage procedure in a secondary thread. |
By default, the WLanguage procedure is executed in the main thread. Observaciones WLanguage procedure executed in the main thread By default, this WLanguage procedure is called in the main thread of the application, with the HFSQL context that corresponds to the procedure: - If the procedure is a local procedure of a window that uses an independent context, the context of the window will be used.
- If the procedure belongs to a component that uses an independent context, the context of the component will be used.
| Caution:
The procedure associated with <Fuente>.Track can be called at any time in the application.
If the procedure reads records or moves between records in the data files, this will have an impact on the application (like the timers).
It may therefore be necessary to use: Multitask must not be used in the procedure code. |
For more details on this procedure, see Parameters of the procedure used by <Fuente>.Track. WLanguage procedure executed in a secondary thread If the WLanguage procedure is called in a secondary thread: - the HFSQL context is copied the first time <Fuente>.Track is called. Only the directories containing the data files in HFSQL Classic mode and/or the connections in HFSQL Client/Server mode are stored.
Remark: If <Fuente>.ChangeDir is called between two calls to the <Fuente>.Track function, <Fuente>.ChangeDir is ignored. Example:
UnFichier.Surveille(hSecondaryThread)
UnAutreFichier.ChangeRep()
UnAutreFichier.Surveille(hSecondaryThread)
- UI elements (windows, controls, etc.) cannot be manipulated in the secondary thread. When a secondary thread must interact with the user or update the UI, it must use a process started from the main thread. This process can correspond to:
- a global procedure of the project or a local procedure (of a window, etc.) called by ExecuteMainThread,
- the "Request for refreshing the display" event of a window run by RequestRefreshUI.
Special cases Watching 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 watched by the server remains the one specified during the call to <Fuente>.Track.
- If the connection is closed, the watch mechanism is automatically stopped.
- Watching continues if the connection is lost then restored by automatic reconnection.
Windows service:
<Fuente>.Track and <Fuente>.TrackStop can be used in a Windows service.
When <Fuente>.Track is used in a Windows service, it can only be tested on the deployed service, and not when testing the service via the "Go" option.
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