Make Calcapl.ave take NULL shapes into account

Summary

Calcapl.ave does not take NULL shapes into account. The NULL shapes get their values from the previous record. The QueryShape request requires that a 'valid' shape object exists first, and in the case of the NULL shapes this is not true; thus, when a value is assigned to the record, it uses the value that already existed in the variable.

Procedure

1. Open a new script window.
   
   
   A. Activate the Project window.
   B. Click the Scripts icon.
   C. Click New.
   
   
2. Copy the following code into the new window.
   
   

   Code:
   '-- Name: View.CalculateFeatureGeometry
   '
   '-- Title:  Calculates feature geometry values
   '        
   '-- Topics:  GeoData
   '
   '-- Description: This is a modified version of calcapl.ave script.
   '-- It calculates area and perimeter for polygon themes and 
   '-- length for line themes. If the view has been projected the 
   '-- calculations are in projected meters. Otherwise the calculations 
   '-- are in native map units. Modify the script to provide
   '-- calculation in the current report units of the view.
   '-- The script processes the list of active themes to calculate
   '-- area and perimeter, or length, depending on the theme type.
   '
   '-- The script will add the fields: Area and Perimeter to polygon
   '-- themes. Length to line themes if they do not exist. If the fields
   '-- exist their values will be recalculated. Rerun the 
   '-- script if you change the projection of the view.
   '
   '-- Requires: A view with at least one active theme. You must have 
   '-- write access to the active theme(s).
   
   '-- Get the view and its projection if any.
   theView = av.GetActiveDoc
   thePrj = theView.GetProjection
   if (thePrj.IsNull) then
     hasPrj = false
   else
     hasPrj = true
   end
   
   '-- Get the list of active themes. if there aren't any,
   '-- let the user know and exit.
   theActivethemeList = theView.GetActivethemes
   if (theActivethemeList.Count = 0) then
     MsgBox.Error("No active themes.","")
     Exit
   end
   
   '-- Loop through the list of active themes. if you can't
   '-- edit the theme inform the user.
   For Each thetheme in theActivethemeList
     theFTab = thetheme.GetFTab
     if (theFTab.CanEdit.Not) then
       MsgBox.Info("Cannot edit table for theme:"++thetheme.AsString,"")
       Continue
     end
   
     '-- Make the FTAB editable and find out the type of feature it is.
     theFTab.SetEditable(TRUE)
     theType = theFTab.FindField("shape").GetType
     if (theType = #FIELD_SHAPEPOLY) then
   
       '-- If it's polygonal check for the existence of the fields
       '-- Area and Perimeter. if they do not exist, create them.
       if (theFTab.FindField("Area") = nil) then
         theAreaField = Field.Make("Area",#FIELD_DOUBLE,16,3)
         theFTab.AddFields({theAreaField})
       else
         ok = MsgBox.YesNo("Update Area?", "Calculate", true)
         if (ok.Not) then
           continue
         end
   
         theAreaField = theFTab.FindField("Area")
       end
   
       if (theFTab.FindField("Perimeter") = nil) then
         thePerimeterField = Field.Make("Perimeter",#FIELD_DOUBLE,16,3)
         theFTab.AddFields({thePerimeterField})
       else
         ok = MsgBox.YesNo("Update Perimeter?", "Calculate", true)
         if (ok.Not) then
           continue
         end
   
         thePerimeterField = theFTab.FindField("Perimeter")
       end
       
       '-- Loop through the FTAB and find the projected area
       '-- and perimeter of each  shape and set the field values
       '-- appropriately.
       For Each rec in theFTab
         theShape = theFTab.ReturnValue(theFTab.FindField("shape"),rec)          
         if(theShape.isNull) then
           theArea = 0.0
           thePerimeter = 0.0        
         else     
           theFTab.QueryShape(rec,thePrj,theShape)  
           theArea = theShape.ReturnArea
           thePerimeter = theShape.ReturnLength
         end
         
         theFTab.SetValue(theAreaField,rec,theArea)
         theFTab.SetValue(thePerimeterField,rec,thePerimeter)
       end
       
     elseif (theType = #FIELD_SHAPELINE) then
   
       '-- If the data source is linear, check for the existence
       '-- of the field "Length". if it doesn't exist, create it.
       if (theFTab.FindField("Length") = nil) then
         theLengthField = Field.Make("Length",#FIELD_DOUBLE,16,3)
         theFTab.AddFields({theLengthField})
   
       else
         ok = MsgBox.YesNo("Update Length?", "Calculate", true)
         if (ok.Not) then
           continue
         end
   
         theLengthField = theFTab.FindField("Length")
       end
        
       '-- Loop through the FTAB and find the projected length of
       '-- each shape and set the field values appropriately. 
       For Each rec in theFTab
         theShape = theFTab.ReturnValue(theFTab.FindField("shape"),rec)
         if(theShape.isNull) then
           theLength = 0
         else                 
           theFTab.QueryShape(rec,thePrj,theShape)
           theLength = theShape.ReturnLength
         end
   
         theFTab.SetValue(theLengthField,rec,theLength)
       end
       
     end 
   
     theFTab.SetEditable(FALSE)
   end
   

   
   
3. Click the Compile button.
   
   
4. Click the Run button.