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Best Practice Makes Perfect

A collaboration with Domino developers about how to do it and how to get it right in Domino

This technique isn't applicable in all situations, but it's a way to make a date or time-based view whose index is only rebuilt when needed, and doesn't require that the date be hardcoded into a design element. The example is intended for use in the Notes mail file, where there's only one user who we're mainly concerned about. It could be used in a shared app context, but in that case it should be set up to use the server's time settings, not the client's as in this example, since different users would be plugging in different formulas and causing constant rebuilds based on their client's settings as opposed to someone else's.
The problem is how to get the view index to be rebuilt only when it is needed, and without "flashing" (i.e. we don't want to open the view and then notice it's out of date). I've been testing this solution and it seems to work.


In the folder, you define a UDC (user-definable column) whose item name is, say "$ZoneDay":

Image:Another way to make an efficient date/based viewImage:Another way to make an efficient date/based view
We use the profile name ColorProfile because the Inbox already contains another UDC with the same profile, and any given view can only use one profile doc for UDCs.


Now, you have to set up the profile document to contain the correct formula for the date-based value you'd like it to display. For this we can use the view's queryopen event, for instance:

Sub Queryopen(Source As Notesuiview, Continue As Variant)
       Dim db As NotesDatabase, sess As New notessession

       Set db = sess.CurrentDatabase

       Dim docPro As NotesDocument, curFormula$, newFormula$, midnight$, gmtMid

       Dim tmpTime As New NotesDateTime("")

       tmpTime.lslocaltime = Today ' which translates to today at midnight.

       gmtMid = tmpTime.LSGMTTime

       midnight = {@ToTime(@Text(@Date(} & Year(gmtMid) & {; } & Month(gmtMid) & {; } & Day(gmtMid) & {; } & Hour(gmtMid) & {; } & Minute(gmtMid) & {; 0)) + " GMT")}

       
       Set docPro = db.GetProfileDocument("colorprofile")

       curFormula = Replace(docPro.GetItemValue("$ZoneDay")(0), Chr$(13), "")

       newFormula = {todayMid := } & midnight & {;

daysOld := (todayMid-PostedDate) / 86400;

@If(daysOld <= 0; "today"; daysOld <= 1; "yesterday"; "older " + @Text(@Integer(daysOld)))}

       If curFormula <> newFormula Then

               docPro.ReplaceItemValue "$ZoneDay", newFormula

               docPro.Save True, False, True

       End If

End Sub


Some comments about this approach:
  • On the line beginning "midnight =", we represent the date by using the @Date function with six arguments. This is done rather than just hardcoding the time constant [mm/dd/yyyy hh:mm:ss GMT] for instance, because we have no way to know the server's date formatting settings. The formula has to be comprehensible by the server, but this code executes on the client, so we can't just format the date as the client would by default.
  • If performance ends up being a problem and you want to find a way to format the date so the server understands it, you might:
    • try using the @TimeMerge function.
    • see whether the format [yyyy/mm/dd hh:mm:ss am/pm] is interpreted the same by all servers (note, however, that "/" might not be universally used as a date delimiter).
    • I'm trying to get a way of representing date/times that's static across all platforms and settings, e.g. as a hex code. I need it for DXL, but as we can see here there are other applications for it.
  • When it's asked to open the view, the view indexer is smart enough to know that if the profile document (colorprofile in this case) has been modified since the view was last opened, that means that a column formula might evaluate differently for existing documents. So it knows in that case to rebuild the view index rather than refreshing. So don't save changes to the profile doc unless you mean it.
  • This approach is doesn't require Designer access for the end user, only enough authority to edit a shared profile document, which they need anyway to edit their own mail preferences. In other applications where users might not have enough muscle to do this, you might need to make the profile document contain an explicit Authors field to allow this access. It could get tricky, which is why I say this might not be applicable for all apps.
  • If you wanted to use the server's timezone settings to determine the day divisions, instead of the client's settings, you can get rid of the timezone stuff and just use the @Date function (you still can't hardcode the date in [brackets] without knowing how the server formats dates).
  • There's an extra argument to @Now to return the server's current time, and you can use that to determine what the server thinks the date is. This is not 100% obvious how to do; I think you'll have to use @Text in your Evaluate call with certain arguments, to get the time in the server's zone.

Andre Guirard | 23 May 2011 04:50:14 PM ET | Home, Plymouth, MN, USA | Comments (5)

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