Introduction to PowerBuilder

Triggering Events Dynamically

Sometimes, events/functions do not exist at compile time. Take the example of writing a generic function (as shown below) which saves DataWindows in a given window. Before saving each DataWindow, this function executes ue_presave event before and ue_postsave after saving the DataWindow. We expect the DataWindow in the passed window to have these events at run-time. In situations like these, we can use the DYNAMIC keyword, so that compiler doesn't check for the existence of the event or function and their arguments & return types.

//Window iWindow datawindow l_dw integer li_NoOfControls, li_Counter, li_RetStatus li_NoOfControls = UpperBound(iWindow.Control[]) For li_Counter = 1 to li_NoOfControls Choose Case iWindow.Control[ li_Counter ].TypeOf() Case DataWindow! l_dw = iWindow.Control[ li_Counter ] If l_dw.ModifiedCount() + & l_dw.DeletedCount() > 0 Then li_RetStatus = l_dw.Event DYNAMIC & TRIGGER ue_PreSave() If li_RetStatus <> 0 Then Return -100 li_RetStatus = l_dw.Update(True) // Error Handling l_dw.Event DYNAMIC ue_PostSave() If li_RetStatus <> 0 Then Return -100 End If Case Else // Other code End Choose Next Return 0

Calling events dynamically is slower than calling static event/functions. That is because, a check is to be done at run-time for event/function existence. So, use DYNAMIC keyword only when necessary.

What happens if an event doesn't exist at run-time when using DYNAMIC keyword? In this matter it works silently. It won't generate any errors that abort the application, instead it returns -1 as the return value. So, make sure you check for the return values.

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