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delphiindy

How to use visual controls in Indy? (Delphi)

My server must print some reports about its work. How can I use visual objects such as labels, edit boxes in the OneEecute event?

Solution

  • The same rule, for not modifying VCL objects in any thread except main thread, is valid here too. You should not change any of VCL controls in OnExecute event-handler, because that code will be run in the context of a worker thread spawn by Indy for every connection.

    If you need to change graphical user interface, do it using Synchronize or Queue methods, or use a custom notification mechanism for notifying the main thread to do the GUI modification for you.

    If you want to call Synchronize or Queue methods, you have to type-cast TIdYarn to TIdYarnOfThread which derives from TIdYarn and implements it with threads:

    // Calling MyMethod using Synchornize inside TIdTcpServer.OnExecute event-handler   
TIdYarnOfThread(AContext.Yarn).Thread.Synchronize(MyMethod);


// Calling MyMethod using Queue inside TIdTcpServer.OnExecute event-handler  
TIdYarnOfThread(AContext.Yarn).Thread.Queue(MyMethod);