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Using Objects to Model Tabular Data

Using Objects to Model Tabular Data. The Story so far. System split into layers – maintainability & re-use Database – queries, tables, rows, columns & parameters Range of objects allowing us to control different parts of the computer using their methods & properties Variables – RAM

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Using Objects to Model Tabular Data

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  1. Using Objects to Model Tabular Data

  2. The Story so far • System split into layers – maintainability & re-use • Database – queries, tables, rows, columns & parameters • Range of objects allowing us to control different parts of the computer using their methods & properties • Variables – RAM • Controls – Interface • DataConnection class – database • Introduced a lot of coding concepts, assignment, sequence, selection, validation, functions, parameters to name a few

  3. Overview of Driving Test 2

  4. How do we Manipulate a List of Data?

  5. Array Lists • Our list of data… • Fred • Wilma • Barney • Betty • The code… • Dim Attendees As New ArrayList • Attendees.Add("Fred") • Attendees.Add("Wilma") • Attendees.Add("Barney") • Attendees.Add("Betty")

  6. The Count Property Dim Attendees As New ArrayList Dim ItemCount As Integer ItemCount = Attendees.Count

  7. Index Numbers • Rather like house numbers • Zero bound (This will drive you mad!) Value Index Fred 0 Wilma 1 Barney 2 Betty 3

  8. RemoveAt Method Value Index Fred 0 Wilma 1 Barney 2 Betty 3 • Attendees.RemoveAt(2) • Which record will be removed?

  9. Changing a List Entry • What will the following do? Attendees.Add("Fred") Attendees.Add("Wilma") Attendees.Add("Barney") Attendees.Add("Betty") Attendees.Item(2) = "Bamm Bamm"

  10. Data Tables • We said all of that to introduce this… • qry_tblAddress_SelectAll • SELECT * • FROM tblAddress

  11. Presentation Layer Code • How do we get at the results of the query?

  12. QueryResults HouseNumber = MyAddresses.QueryResults.Rows(1).Item("HouseNo") Street = MyAddresses.QueryResults.Rows(3).Item("Street") AddressNo = MyAddresses.QueryResults.Rows(0).Item("AddressNo") DateAdded = MyAddresses.QueryResults.Rows(3).Item("Active") CountyCode = MyAddresses.QueryResults.Rows(1).Item(“HouseNo") CountyCode = MyAddresses.QueryResults.Rows(4).Item(“CountyCode")

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