DataFlex

Subtract One MessageSet from Another

Demonstrates the Chilkat MessageSet.Subtract method, which removes from this set every identifier whose numeric value is also present in another MessageSet. The only argument is the other set. This example starts with ids 1:10, subtracts 2,4,6, and prints what remains.

Background: A common IMAP pattern is "process everything except what I've already handled." Subtract makes that a single call: remove the already-processed ids from a working set. The comparison is numeric only and this object's HasUids is preserved, so for meaningful results both sets should hold the same id type from the same mailbox. Passing the same object clears the set; passing an empty set changes nothing.

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DataFlex

Use ChilkatAx-win32.pkg

Procedure Test
    Boolean iSuccess
    Handle hoMsgSet
    Variant vProcessed
    Handle hoProcessed
    String sRemaining
    String sTemp1

    Move False To iSuccess

    //  Demonstrates the MessageSet.Subtract method, which removes from this set every identifier
    //  that is also present in another MessageSet.  The only argument is the other MessageSet.

    Get Create (RefClass(cComChilkatMessageSet)) To hoMsgSet
    If (Not(IsComObjectCreated(hoMsgSet))) Begin
        Send CreateComObject of hoMsgSet
    End

    //  Start with messages 1 through 10.
    Get ComFromCompactString Of hoMsgSet "1:10" To iSuccess
    If (iSuccess = False) Begin
        Get ComLastErrorText Of hoMsgSet To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    //  The identifiers that have already been processed and should be excluded.
    Get Create (RefClass(cComChilkatMessageSet)) To hoProcessed
    If (Not(IsComObjectCreated(hoProcessed))) Begin
        Send CreateComObject of hoProcessed
    End
    Get ComFromCompactString Of hoProcessed "2,4,6" To iSuccess
    If (iSuccess = False) Begin
        Get ComLastErrorText Of hoProcessed To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    //  Remove the already-processed identifiers from msgSet.
    Get pvComObject of hoProcessed to vProcessed
    Send ComSubtract To hoMsgSet vProcessed

    //  Show what remains.
    Get ComToCompactString Of hoMsgSet To sRemaining
    Showln sRemaining
    //  Output: 1,3,5,7:10


End_Procedure