WrapperRDD Class

This class can be used to wrap an existing RDD and add some functionality to it, such as logging, encryption etc.
To use it, create a subclass of this class and implement the methods that you want to override.
The constructor of this class takes an existing RDD object and automatically replaces it in the Workarea table.

Inheritance Hierarchy

Object
WrapperRDD

Namespace: XSharp.RDD
Assembly: XSharp.Core (in XSharp.Core.dll) Version: 2.19

Syntax

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 CLASS WrapperRDD IMPLEMENTS IRdd

public class WrapperRDD : IRdd

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The WrapperRDD type exposes the following members.

Constructors

	Name	Description
	WrapperRDD	Initializes a new instance of the WrapperRDD class

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Properties

	Name	Description
	Alias	Retrieve the alias name.
	Area	Retrieve the Workarea number.
	BoF	Is the table at the logical beginning-of-file.
	Deleted	Is the current row deleted?
	Driver	Driver (RDD) name of the object.
	EoF	Is the table at the logical end-of-file.
	Exclusive	Is the Workarea opened Exclusively
	FieldCount	The # of fields in the current Workarea.
	FilterText	The filter condition as a string.
	Found	The outcome of the last search operation.
	RecCount	The number of rows.
	RecId	The row identifier at the current cursor position.
	RecNo	The physical row identifier at the current cursor position.
	Shared	Is the current Workarea opened Shared?

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Methods

	Name	Description
	AddField	Add a column.
	Append	Append a blank row and position the cursor to the new row.
	AppendLock	Add a newly appended row to the list of locked rows.
	BlobInfo	Retrieve information about a memo column.
	ChildEnd	Report the initialization of a relation.
	ChildStart	Report the initialization of a relation.
	ChildSync	Post a pending relational movement, indicating that the specified child work area has been affected by a parental movement.
	ClearFilter	Clear the active filter condition.
	ClearRel	Clear relations.
	ClearScope	Clear the active locate condition.
	Close	Close a table.
	CloseMemFile	Close the memo file
	Compile	Compile an expression.
	Continue	Goto the next record based on the corrent locate condition.
	Create	Create a table.
	CreateFields	Add columns defined in an array.
	CreateMemFile	Create the memo file
	DbEval	Evaluate a code block for each row.
	DebuggerDisplay
	Delete	Mark the row at the current cursor position for deletion.
	EvalBlock	Evaluate a code block.
	FieldIndex	Return the ONE based field index for a field name.
	FieldInfo	Retrieve and optionally change information about a column.
	FieldName	Retrieve a column name based on its ONE based column number.
	Flush	Flush the changes to the table, its indexes and memo file.
	ForceRel	Force all pending relational seeks to be performed.
	GetField	Retrieve the field information for a column based on its ONE based column number.
	GetRec	Retrieve the RDD's record buffer as array of bytes.
	GetScope	Retrieve the active locate condition.
	GetValue	Get a value for the specified column.
	GetValueFile	Get the value for a column and write (export) it to an external file.
	GetValueLength	Get the length of the for the specified column.
	GoBottom	Position the cursor to the last logical row.
	GoCold	Write the contents of a work area's memory to the data store (usually a disk).
	GoHot	Mark a data buffer as hot, indicating that it needs to be written to the data store.
	GoTo	Position the cursor to a specific, physical row.
	GoToId	Position the cursor to a specific, physical identity.
	GoTop	Position the cursor to the first logical row.
	HeaderLock	Lock or unlock the header of a database file.
	Info	Retrieve and optionally change information about a work area.
	Lock	Perform a lock.
	Open	Open a table.
	OpenMemFile	Open the memo file
	OrderCondition	Set the condition for the next Index Creation
	OrderCreate	Create a new index or tag.
	OrderDestroy	Delete an index or tag.
	OrderInfo	Retrieve information about an index.
	OrderListAdd	Open an index file and add to the list of open indexes for the current Workarea.
	OrderListDelete	Close an index file and remove it from the list of open indexes for the current Workarea.
	OrderListFocus	Set focus to another index in the list open indexes for the current Workarea.
	OrderListRebuild	Rebuild all indexes for the current Workarea.
	Pack	Physically remove rows marked for deletion.
	PutRec	Replace the row at the current cursor position with the contents of a byte array.
	PutValue	Write a value for a specified column
	PutValueFile	Read (Import) a value from an external file and write it to the specified column.
	Recall	Remove the deletion marker from the row at the current cursor position.
	RecInfo	Retrieve and optionally change information about a row.
	Refresh	Discard all changes to the current record and reread the buffer from disk. When the current buffer is in Append mode then the server will move to the bottom of the file.
	RelArea	Retrieve the logical number of a related work area.
	RelEval	Evaluate a code block against the relation in a work area.
	RelText	Retrieve the key expression of a relation.
	Seek	Perform a seek operation on the current selected index for the current Workarea.
	SetFieldExtent	Set the Number of Fields the AddField Method will add.
	SetFilter	Set the filter condition.
	SetRel	Set a relation.
	SetScope	Set the locate condition.
	Skip	Position the cursor relative to its current position.
	SkipFilter	Position the cursor, respecting scope and filter conditions.
	SkipRaw	Position the cursor regardless of scope and filter conditions.
	SkipScope	Position the cursor relative to its current position within the current scope.
	Sort	Physically reorder a table.
	SyncChildren	Force relational movement in child work areas to synchronize them with the parent work area.
	Trans	Copy one or more rows from one work area to another.
	TransRec	Copy a single row from one work area to another.
	UnLock	Release locks.
	Zap	Physically remove all rows from a table.

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Examples

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 1CLASS MyRDD Inherit XSharp.RDD.WrapperRDD
 2
 3CONSTRUCTOR(oRdd as XSharp.RDD.IRDD)
 4   SUPER(oRdd)
 5
 6VIRTUAL METHOD GetValue(nFldPos AS LONG)        AS OBJECT
 7   Log("Reading field "+nFldPos:ToString())
 8   RETURN SUPER:GetValue(nFldPos)
 9
10VIRTUAL METHOD PutValue(nFldPos AS LONG, oValue AS OBJECT) AS LOGIC
11   Log("Writing field "+nFldPos:ToString()+" value "+oValue:ToString())
12   RETURN SUPER:PutValue(nFldPos, oValue)
13END CLASS
14
15FUNCTION Start() AS VOID
16   // Open customer table
17   USE Customer NEW
18
19   // Get current RDD for the selected Workarea
20   VAR oRdd := XSharp.RuntimeState.Workareas:GetRDD(Select())
21
22   // Create Wrapper RDD. This automatically replaces the RDD in the Workarea table
23   oRdd := MyRDD{oRdd}
24
25   ? FieldGet(1)           // This should also call Log() to show reading the value
26   ? FieldPut(1,"Jones")   // This should also call Log() to show writing the value
27   DbCloseArea()
28   RETURN
29
30Function Log(cMessage as STRING) AS VOID
31   ? cMessage
32   RETURN

Reference

XSharp.RDD Namespace