1. Collections, Arrays & Iteration
Mike Feltman
F1 Technologies

2. Agenda
 Collections in VFP
 Working with Collections
 Writing Better Code with Collections
 Using Collections for Object Manipulation
 Adding Power to VFP Arrays
 Collections vs. Arrays
 Merging Arrays & Collections

3. Who Am I
 President F1 Technologies since 1990
 Co-author Visual FoxExpress
 Consultant
 Xbase Developer since dBase III/FoxBase
1987

4. “Objects” Collections in VFP
 _SCREEN, _VFP, FormSet,
DataEnvironment, Toolbar, Container,
PageFrame, Page, Grid, Column,
CommandGroup, OptionGroup, Container,
Custom, Control

5. Other Collections in VFP
 _VFP
 Forms
 Projects
 Project
 Files
 Servers
 XMLAdapter
 Tables
 XMLTable
 Fields

6. “Pseudo” Collections in VFP
 _SCREEN.Controls  _SCREEN.Forms
 Form.Controls  FormSet.Forms
 Custom.Controls  CommandGroup.Buttons
 Control.Controls  OptionGroup.Buttons
 Toolbar.Controls  PageFrame.Pages
 Container.Controls  Grid.Columns
 Column.Controls

7. The Collection Class
 New in VFP 8
 Key Properties
 Count
 KeySort (0-3)
 Key Methods
 Add(eItem, cKey, eBefore, eAfter)
 Item(eIndex)
 GetKey(eIndex)

8. Iterating Collections
 FOR lnI = 1 TO loCollection.Count
 FOR EACH loObject in loCollection
 FOR EACH loObject in loCollection
FOXOBJECT
 Examples: Iterate1.prg, Iterate2.prg,
Iterate3.prg

9. UI Support for Collections
 Listbox
 ComboBox
 Example: CollectionDemo.SCX

10. Writing Better Code with
Collections
 Problem: This.Parent.Page2.txtCompany
creates a tightly coupled dependency.
 Solution: Dynamically retrieved Object
references eliminate tight coupling.
 o=o(…) or o=f(…)

11. Using Collections for Multiple
Object Manipulations
 AC
 CC
 WC

12. Returning an Array
 From within a class method a member
array can be used as the return value.
 A function can return an array by calling a
class method that returns an array.
 Example: aConcact in utility.prg

13. Array Utilities
 aCompact
 aConcat
 aFirst
 aJoin
 aLast
 aReverse
 aUnique
 aWithout
 ArrayDemo.Prg

14. Wrapping an Array in a Collection
 Fox Data Objects – ADO / LINQ like
 DataCollection.prg, cDataCollection of
cData

15. Conclusion
 Collections in VFP provide convenient ways to
access objects
 Retrieving object references from collections can
make code a lot more flexible and stable
 VFP has a lot of powerful options available on
arrays
 Collection and array implementations are just
different enough that each has their own place.