Re: [Metakit] On-the-fly data structures and nested views

[Brian Kelley]

Kim Bachman wrote: To make things worse, I need the ability to add/remove properties from the item data on a per item basis at run time.  The item data could include one or more of hundreds of properties.   ItemView     Item[Name:S,Description:S,Number:I...]         ItemDataView             ItemData[Date:I,Time:I,Style:I,Size:I...]             ...             ItemData[Date:I,Time:I,Style:I,Size:I...]       Item[Name:S,Description:S,Number:I...]         ItemDataView             ItemData[Date:I,Type:I,Length:I,Color:I...]             ...             ItemData[Date:I,Type:I,Length:I,Color:I...]     1. Is this possible in Metakit? Yes.  Get rid of ItemView and have Item in different tables.  Let's assume that in your table "Name" is unique across all items.  You will need some unique identifier for the following technique to work.  If name as unique we can generate an "items" table which knows which underlying table a given item lives in.  The underlying tables can have different properties and subviews but all should have an unique column Name. The idea is when looking up an object first find the name in the items table.  From the items table find out the name of the subtable, retrieve this view and then look up Name in the subtable. You'll have to forgive my python style pseudo code here.  itemtable = st.getas("items[Name:S,table:S]") itemtype1 = st.getas("itemtype1[Name:S.Description:S,Number:I...,data[Date:I,Time:I,Style:I,Size:I]") itemtype2 = st.getas("itemtype2[Name:S.Description:S,Number:I...,data[Date:I,Type:I,Length:I,Color:I...]") # we'll create two objects named "object1" and "object2" that live in the seperate tables itemtype1 itemtype2 itemtable.append(("object1", "itemtype1")) itemtable.append(("object2", "itemtype2")) # add some data to the objects index = itemtype1.append(("object1", ...)) # add some properties to the subview itemtype1[index].data.append(record1)) itemtype1[index].data.append(record2)) index = itemtype2.append(("object2", ...)) ... now the dispatch method to find the appropriate subtable The dispatcher finds a given item with name Name from itemtable and retrieve the appropriate row from the subtables #first find out which table belongs to the item index = itemtable.find(Name=Name) if index == -1: Error, cannot find item row = itemtable[index] #retrieve the proper table table = st.view(row.table) # the subtables can be restructured on the fly with new properties ect... # find the proper row index = table.find(Name=Name) if index == -1: Error, Name doesn't exist in the table! # get the row row = table[index] # play with the row :) for data in row.data:       ...