SCATTER & GATHER Commands Have a New NAME Argument

• Microsoft Visual FoxPro for Windows, version 3.0

SUMMARY

The SCATTER and GATHER commands have a new argument (NAME <ObjectName>) that enables the Object Oriented Programming (OOP) features of Visual FoxPro. This article shows by example how to use this new argument.

MORE INFORMATION

SCATTER Command

SCATTER NAME <ObjectName> creates a row or record type of object with properties that have the same name as the fields in the table. The values of the properties are initialized to the same value as that of the fields in the table. General and memo field types do not have a property created for them in the object.

The syntax for the SCATTER command is:

SCATTER

  [FIELDS <FieldNameList>
  | FIELDS LIKE <Skeleton> | FIELDS EXCEPT <Skeleton>][MEMO]
  TO <ArrayName> | TO <ArrayName> BLANK | MEMVAR | MEMVAR BLANK
  | NAME <ObjectName>

GATHER Command

GATHER NAME <ObjectName> writes a row or record of values from the object to the table where the object properties have names that are identical to the table field names.

The syntax for the GATHER command is:

GATHER FROM <ArrayName> | MEMVAR | NAME <ObjectName>

  [FIELDS <FieldList> | FIELDS LIKE <Skeleton>
  | FIELDS EXCEPT <Skeleton>]
  [MEMO]

Code Sample

The following code defines a custom class that uses the SCATTER and GATHER commands with their object argument, NAME. The code demonstrates:

• How to create the class.
• How to instantiate the object from the class.
• How to use SCATTER NAME and GATHER NAME to read and write to a table through an object.
• How to send messages to the object to access properties of the object.

ACTIVATE SCREEN CLEAR CLOSE DATABASES

* The next three commands create a new table and add two new records * with values.

CREATE TABLE test1 (Name C(10), Age N(3)) INSERT INTO test1 (Name,Age) ;

                VALUES ('John Doe',43)

                VALUES ('Jane Smith',29)

* The following command creates a new object 'oTable' from the custom * class 'Table' defined at the end of this program. It uses the table * 'test1' that was just made. The object 'oRow' is automatically * created during the creation of oTable from the SCATTER NAME <object> * command and has a property created for each field in the table.

oTable=CREATEOBJECT('Table','test1') LIST

* The following command sends a message to the object oTable to run the * method Next which moves the record pointer in the table ahead one.

oTable.Next()

* The next two commands send messages to assign new values to the * properties of oTable.oRow.

oTable.oRow.Name='New Name' oTable.oRow.Age=1

* Note that the following command is calling the user defined Gather * function or method which then calls the GATHER NAME command.

oTable.Gather()

* The following sends a message to object oTable to run the method Previous * and assign new values to properties before writing them to the * table 'test1.dbf' with GATHER NAME command.

oTable.Previous() oTable.oRow.Name='VFP' oTable.oRow.Age=0 oTable.Gather() LIST RETURN

***************************

*** Class Definition    ***

DEFINE CLASS Table AS Custom

* The keyword PROTECTED scopes the methods, properties and * objects making them only accessible to methods in the * current class definition.

PROTECTED cFileName cFileName='' oRow=''

* The Init event runs each time a new object is instantiated * from its class.

PROTECTED FUNCTION Init(tcFileName)

   * tcFileName: second parameter of CreateObject command,
   * which is the name of the file to open.
   SELECT 0
   * Open the file in the next available workarea.
   this.Open(tcFileName)
   * Note that the following command is calling the user
   * defined Scatter method, which then calls the
   * SCATTER NAME command.
   this.Scatter()
   RETURN .T.

FUNCTION Open(tcf)

   * tcf: the filename to open.
   USE (tcf)
   RETURN .T.

FUNCTION Close

   USE
   RETURN .T.

FUNCTION Next

   IF NOT EOF()
      SKIP
   ENDIF
   IF EOF() AND NOT BOF()
      SKIP -1
   ENDIF
   this.Scatter()
   RETURN .T.

FUNCTION Previous

   IF NOT BOF()
      SKIP -1
   ENDIF
   this.Scatter()
   RETURN .T.

FUNCTION Scatter

   * SCATTER NAME <objectname>
   * In Visual FoxPro only, creates an object
   * the properties of which have the same names as
   * the fields in the table. The values of each
   * of the object's properties are the contents
   * of the fields in the table.

   SCATTER NAME this.oRow MEMO
   RETURN .T.

FUNCTION Gather

   * GATHER NAME <objectname>
   * Specifies an object the properties of which
   * have the same names as fields in the table.
   * The contents of each field are replaced by
   * the value of the property with the same
   * names as the fields.

   GATHER NAME this.oRow MEMO
   RETURN .T.

FUNCTION Destroy

   this.Close()
   RETURN .T.

ENDDEFINE * End of code sample