Microsoft KB Archive/130306

= Save/SET/Restore of SET Environment Settings =

Article ID: 130306

Article Last Modified on 2/10/2000

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APPLIES TO


 * Microsoft Visual FoxPro 3.0 Standard Edition

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This article was previously published under Q130306



SUMMARY
In version 2.x, environment settings such as "DELETED" were often stored into memory variables at the beginning of a section of code. At the end, the settings were manually reassigned to the original value. This article demonstrates an object-oriented approach to saving and restoring environment settings.



MORE INFORMATION
The class "cSET" demonstrates this technique. In this class, a number of the current SET environment settings for DELETED, ALTERNATE, and DECIMALS are stored in objects. One object is created for each environment setting that should be stored. This class could easily be expanded to include additional environment settings.

When the class, cSET, is instantiated in your form or other application component, an object is created for each desired environment setting. The CONSTRUCTOR method is invoked whenever you want to change an environment setting. It creates a command string that sets the desired temporary environment setting. When the instantiated class object is released, the DESTRUCTOR method is called. This method restores each environment setting to its state at the time cSET was instantiated.

  To use this approach in an application, begin by creating a program that contains the class definition. * Begin code example * Save This as CSET.PRG * This class provides SET environment save/SET/restore capabilities * When the class is instantiated, the current SET environment is  * saved & SET to the desired value. When the instantiated object goes * out of scope, the environment is restored.

* Usage: * CreateObject( "CSET", ,  |  [, ] ) *  *   cExpr1 = One of the SET commands *  cExpr2 = Appropriate character value for the SET command *  nExpr2 = Appropriate numeric value for the SET command *  cExpr3 = Optional character value for SET commands that are both *           ON | OFF *           and have another value (like ALTERNATE, FIELDS, etc.) *  * Examples: *  loDeletedSave   = createobject( "CSET", "deleted", "on" ) *  loDecimalsSave  = createobject( "CSET", "decimals", 5 ) *  loAlternateSave = createobject( "CSET", "alternate", "on", ;   *                     "alter.txt")

DEFINE CLASS CSET AS CUSTOM

* PROTECTED Data Members * =====================================================  PROTECTED mcSET               && SET command PROTECTED muOrgValue         && Original value of the SET PROTECTED muOrgValue1        && Original secondary value of the SET

* Public Data Members * ========================================================  * NONE

* PROTECTED Function Members * =================================================

* Constructor Method * --

PROTECTED FUNCTION Init PARAMETER pcSET, puNewValue, pcNewValue1

LOCAL lnParmCount         && number of PARAMETERs sent to init LOCAL lcSETCommand           && constructed SET command

lnParmCount = PARAMETERS

* Default the data members This.mcSET = "" This.muOrgValue = "" This.muOrgValue1 = ""

IF ( lnParmCount < 2 ) *  This.error( "some error" ) RETURN ENDIF

* Save current environment

This.mcSET      = pcSET This.muOrgValue = SET( pcSET ) This.muOrgValue1 = SET( pcSET, 1 ) IF ( This.muOrgValue == This.muOrgValue1 ) * throw This away because we don't need it     This.muOrgValue1 = "" ENDIF

IF ( lnParmCount = 3 ) * optional argument handling lcSETCommand = pcSET + " to " + pcNewValue1 SET &lcSETCommand ENDIF

IF ( TYPE( "This.muOrgValue" ) == 'C' ) * character type of SET lcSETCommand = puNewValue IF ( ! INLIST( This.muOrgValue, "ON", "OFF" ) ) * not a simple ON|OFF so add a TO keyword lcSETCommand = "TO " + puNewValue ENDIF ELSE * numeric type of SET lcSETCommand = "TO " + STR( puNewValue ) ENDIF

lcSETCommand = pcSET + " " + lcSETCommand SET &lcSETCommand                         && change the SET

* Destructor Method * --   PROTECTED function Destroy

*LOCAL lcSETCommand           && constructed SET command

IF ( EMPTY( This.mcSET ) ) RETURN ENDIF

IF ( TYPE( "This.muOrgValue" ) == 'C' ) * character type of SET lcSETCommand = This.muOrgValue IF ( ! INLIST( This.muOrgValue, "ON", "OFF" ) ) * not a simple ON|OFF so add a TO keyword lcSETCommand = "TO " + This.muOrgValue ENDIF ELSE * numeric type of SET lcSETCommand = "TO " + STR( This.muOrgValue ) ENDIF

lcSETCommand = This.mcSET + " " + lcSETCommand SET &lcSETCommand                             && restore the SET

IF ( ! EMPTY( This.muOrgValue1 ) ) * restore secondary SET information lcSETCommand = This.mcSET + " TO " + This.muOrgValue1 SET &lcSETCommand ENDIF

* Public Function Members * ====================================================

* Value Method * ---

* RETURN the current values of the PROTECTED data members in a comma * delimited string.

FUNCTION Value LOCAL lcRETURNValue

IF ( TYPE( "This.muOrgValue" ) == 'C' ) lcRETURNValue = This.mcSET + "," + This.muOrgValue ELSE lcRETURNValue = This.mcSET + "," + ; ALLTRIM( STR( This.muOrgValue ) ) ENDIF

IF ( ! EMPTY( This.muOrgValue1 ) ) lcRETURNValue = lcRETURNValue + "," + This.muOrgValue1 ENDIF

RETURN lcRETURNValue

ENDDEFINE

*** END CODE EXAMPLE FOR cSET.PRG   Create a program with the following code. This code would normally be placed in the load event of a form, or at the top of a .PRG file. For the purposes of demonstration, it is being placed in a separate program file: ******************************************************************  *Begin code example ******************************************************************

* Driver program to test CSET class

SET PROCEDURE TO cset ADDITIVE

CLEAR SET DELETED ON      && start it out on for testing

_Screen.Show ? "Deleted:", SET("deleted") loDeletedSave = CreateObject( "CSET", "deleted", "off" ) ? "Value:", loDeletedSave.Value ? "Deleted:", SET("deleted")

  Run the program created in step 2. The following values should be displayed on the screen:   Deleted: ON   Value: deleted, ON   Deleted: OFF 

Additional query words: VFoxWin

Keywords: kbcode KB130306

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