FoxDataObjects - Object-Relational Mapping Tool for Visual FoxPro

fdoCollection Class
FoxDataObjects	Object-Relational Mapping Tool for Visual FoxPro®

The fdoCollection is an easy to use collection class specially designed to implement one-to-many and many-to-many relationships, as of collection of simple values in your business classes. Although Visual FoxPro 8 (and up) features a basic Collection class, the fdoCollection class provides an extra number of functions and features that simplifies object relationships management, implement collection-level events, provides a way to easily access modified/added and even removed item, optimizes memory usage and accelerate referenced instances loading with a powerful collection-level lazy loading mechanism.

As any other collection, the fdoCollection class exposes the Count and Item properties, along with Add, Remove and Clear methods. It can be used to store objects references or simple values. With object references, it provides specialized methods that allows to know whether a specific reference has been loaded (for lazy loaded references), the original count value and referenced objects identifiers when the holder object was retrieved or last saved into the database, separated list of added, modified and removed items, and much more. It also provides a complete set of events or procedure-hooks that are automatically called when the collection initializes, destroys, clears; or items are added or removed.

The following tables shows the properties and methods exposed by the fdoCollection class. This class can be sub-classed in order to implement specific collection level functionality appropriate for your business classes.

Properties

AddedCount	AddedItem	Count
Errors	EventsEnabled	HasChanged
Item	ModifiedCount	ModifiedItem
OldCount	OldItem	Owned
ReferencedClass	RemovedCount	RemovedItem
Type

Methods

Add	Average	Clear
Contains	IndexOf	InsertAt
IsItemLoaded	IsItemModified	IsItemNew
KeyOf	Remove	RemoveAt
ResetChanges	Sum

Events

AfterAdded	AfterChanged	AfterCleared
AfterFilled	AfterInserted	AfterRemoved
AfterSaved	BeforeAdd	BeforeClear
BeforeFill	BeforeInsert	BeforeRemove
BeforeReplace	BeforeSave	OnDestroy
OnInit

Example

DEFINE CLASS Invoice AS CONTAINER

InvNumber=0

InvDate=Date()

Customer=.NULL.

Total=0.0000

ADD OBJECT lines AS fdoCollection WITH ReferencedClass="InvoiceLine"

PROCEDURE OnSave (oSession)

? "Actual invoice lines:",This.Lines.Count

? "Modified Lines:",This.Lines.ModifiedCount

? "-----------------------------------------"

FOR EACH oItem IN THIS.Lines.ModifiedItem

? oItem.Product.Code,oItem.Product.Description, oItem.Quantity

ENDFOR

? "Added Lines:",This.Lines.AddedCount

? "----------------------------------"

FOR EACH oItem IN THIS.Lines.AddedItem

? oItem.Product.Code,oItem.Product.Description, oItem.Quantity

ENDFOR

? "Removed Lines:",This.Lines.RemovedCount

? "----------------------------------"

FOR EACH oItem IN THIS.Lines.RemovedItem

? oItem.Product.Code,oItem.Product.Description, oItem.Quantity

ENDFOR

? "Original invoice lines:",This.Lines.OldCount

FOR EACH oItem IN THIS.Lines.OldItem

? oItem.Product.Code,oItem.Product.Description, oItem.Quantity

ENDFOR

ENDPROC

ENDDEFINE

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