1 Reply Latest reply on Oct 2, 2010 9:12 AM by johnrellis

    Riddle: When is an LrTasks.pcall not an LrTasks.pcall???

    areohbee Level 6

      I have the following code to transfer metadata from one image to another:



                      local sts, val = LrTasks.pcall( fromPhoto.getFormattedMetadata, fromPhoto, k )
                      if sts then
                          sts, msg = LrTasks.pcall( toPhoto.setRawMetadata, toPhoto, k, val ) -- this pcall does not seem to work - error caught
                          -- in calling context for some reason.
                          if not sts then
                              RcUtils.logError( LOC( "$$$/X=Unable to set raw metadata using '^1' as key and '^2' as value, error message: ^3", k, val, msg ) )
                          RcUtils.logError( LOC( "$$$/X=Unable to get formatted metadata using '^1' as key, error message: ^2", k, val ) )



      get-formatted-metadata errors are trapped by the pcall, but set-raw-metadata errors are not (they always propagate to the calling context).





        • 1. Re: Riddle: When is an LrTasks.pcall not an LrTasks.pcall???
          johnrellis Most Valuable Participant

          Have you tried using the Lua pcall() rather than LrTasks.pcall()?  The documentation of LrTasks.pcall says:


          Simulates Lua's standard pcall(), but in a way that allows a call to LrTasks.yield() to occur inside it.


          but in what actual instances would it be desirable to use one version of the other?  I'm wondering in your case if there s some subtlety (or LR bug) caused by an attempt of setRawMetadata() to call yield()?


          If pcall() doesn't catch the error, you might try LrFunctionContext.callWithContext() with a context:addCleanUpHandler() -- that seems to catch everything.