TRDD / TRDDODBC

Fonte: source/classes/trdd.prg, source/classes/trddodbc.prg

TRDD is a standalone base class. TRDDODBC inherits from: TRDD

TRDD is a virtual RDD (Replaceable Database Driver) base class that delegates RDD operations to code blocks. TRDDODBC extends TRDD to provide an ODBC-backed RDD, allowing standard USE, SKIP, APPEND, SEEK, and field access commands against ODBC data sources. It registers as the "ODBC" RDD via RddRegister.

Key DATA Members (TRDD)

DATA	Type	Description
`bAddField`	Block	Code block for adding a field definition
`bAppend`	Block	Code block for appending a blank record
`bGetValue`	Block	Code block for reading a field value
`bPutValue`	Block	Code block for writing a field value
`bSkip`	Block	Code block for moving the record cursor
`bOpen`	Block	Code block for opening a table
`bCloseArea`	Block	Code block for closing a work area
`bBof`	Block	Code block for beginning-of-file check
`bEof`	Block	Code block for end-of-file check
`bRecCount`	Block	Code block for record count
`bRecNo`	Block	Code block for current record number
`bGoTop`	Block	Code block for GoTop

TRDD Methods

Method	Description
`New()`	Create the virtual RDD with default code blocks
`SetRdd()`	Register this instance as the active virtual RDD
`AddField( nArea, nField )`	Add a field via bAddField code block
`AddFields( pArea, aFields )`	Add multiple fields using RddSetFieldExtent / RddAddField
`Open( pArea, nArea, cFileName, cAliasName, lShared, lReadOnly )`	Open a table via bOpen
`Skip( pArea, nArea, nRecs )`	Skip records via bSkip
`CloseArea( nArea )`	Close a work area via bCloseArea

TRDDODBC

DATA	Type	Description
`oOdbc`	Object (CLASSDATA)	Shared TOdbc connection instance
`aDbOdbc`	Array[255]	Array of open TDbOdbc objects indexed by work area

Method	Description
`New( cDSN, cUserName, cPassword )`	Create ODBC connection and register as virtual RDD
`End()`	Close all open work areas and disconnect ODBC
`Open( pArea, nArea, cFileName, cAliasName, lShared, lReadOnly )`	Open an ODBC table; creates TDbOdbc and registers fields
`CloseArea( nArea )`	Close a specific work area
`GetValue( pArea, nArea, nField )`	Read a field value via FieldGet
`PutValue( pArea, nArea, nField, cType, uValue )`	Write a field value via PutValue
`Append( nArea )`	Append a blank record
`Delete( pArea, nArea )`	Delete the current record
`Seek( pArea, nArea, cExpSearch, lSoftSeek )`	Seek for a value
`Skip( pArea, nArea, nRecs )`	Move the record cursor
`GoTop / GoBottom / GoToId`	Cursor navigation
`FieldInfo( pArea, nArea, nField, nInfoType )`	Get field metadata
`OrdCreate / OrdInfo / OrdListAdd / OrdListClear / OrdListFocus`	Order management (delegated to TDbOdbc)

Example: USE Table via ODBC RDD

#include "FiveWin.ch"

function Main()

   local oRdd := TRDDODBC():New( "MyDSN", "user", "pass" )

   REQUEST ODBC

   USE customers VIA "ODBC" ALIAS CUST

   DO WHILE ! CUST->( Eof() )
      ? CUST->Name, CUST->City
      CUST->( Skip() )
   ENDDO

   CUST->( dbCloseArea() )
   oRdd:End()

return nil

Notes