Code Comparison: Visual FoxPro Grid & Clipper/DOS TbrowseLast reviewed: April 30, 1996Article ID: Q130439 |
The information in this article applies to:
SUMMARYCA-Clipper version 5.x has five predefined classes built into its language. One of these is the Tbrowse class, which is similar to Visual FoxPro's Grid class. This article compares the two. NOTE: This article only describes how to create a Grid control in a program. Grids can also be created visually through drag-drop and the Visual Class Designer.
MORE INFORMATIONClipper actually provides two Tbrowse classes - TbrowseDB() and TbrowseNew(). TbrowseDB() browses tables, and TbrowseNew() browses other data sources, such as text files and arrays. Below are comparisons of how to browse a table that contains three columns. In each comparison, the Clipper code is shown followed by the equivalent program in Visual FoxPro. NOTE: Run the following program first to create the TEST table used in the comparisons.
*** Code to create the TEST table ***
&& In Clipper, execute these 5 lines:
&& aDbf := {}
&& AADD(aDbf, { "Fld1", "N", 3, 0 })
&& AADD(aDbf, { "Fld2", "C", 4, 0 })
&& AADD(aDbf, { "Fld3", "C", 20, 0 })
&& DBCREATE("Test",aDbf)
&& In FoxPro, execute the next line:
&& CREATE TABLE Test (fld1 n(3),fld2 c(4),fld3 c(20))
USE Test
FOR i=1 TO 50
APPEND BLANK
REPLACE Fld1 WITH i
REPLACE Fld2 WITH ALLTRIM(STR(i))
REPLACE Fld3 WITH REPLICATE(CHR(64+i),20)
NEXT
CLOSE ALL
*** End of code to create TEST table ***
Clipper
#include "inkey.ch"
#include "setcurs.ch"
#define MYCOLORS "BG/B,RB+/W,W/N,N,GR+/W,G+/B,R+/B,GR+/B"
#define HEADSEP CHR(205) + CHR(209) + CHR(205)
#define COLSEP CHR(32) + CHR(179) + CHR(32)
FUNCTION Main()
LOCAL b, column, nKey
SET SCOREBOARD OFF
SET DATE BRITISH
SET CONFIRM ON
USE test
SETCURSOR(SC_NONE)
SETCOLOR("N/W")
SCROLL()
SETCOLOR("BG/B,RB+/W,,,BG/N")
SCROLL( 2, 6, 22, 72 )
@ 2, 6 TO 22,72 DOUBLE
b := TBrowseDB( 3, 7, 21, 71 )
b:colorSpec := MYCOLORS
b:colSep := COLSEP
b:headSep := HEADSEP
// Custom Skipper
b:skipBlock := {|nRecs| Skipper( nRecs )}
// TBColumn objects
column := TBColumnNew( "Field 1", {|| test->fld1} )
b:addColumn( column )
column := TBColumnNew( "Field 2", {|| test->fld2} )
b:addColumn( column )
column := TBColumnNew( "Field 3", {|| test->fld3} )
b:addColumn( column )
WHILE .T.
WHILE ( !b:stabilize() )
nKey := INKEY()
IF ( nKey != 0 )
EXIT
ENDIF
END
IF ( b:stable )
nKey := INKEY(0)
ENDIF
// Process key
IF ( nKey == K_DOWN )
b:down()
ELSEIF ( nKey == K_UP )
b:up()
ELSEIF ( nKey == K_PGDN )
b:pageDown()
ELSEIF ( nKey == K_PGUP )
b:pageUp()
ELSEIF ( nKey == K_CTRL_PGUP )
b:goTop()
ELSEIF ( nKey == K_CTRL_PGDN )
b:goBottom()
ELSEIF ( nKey == K_RIGHT )
b:right()
ELSEIF ( nKey == K_LEFT )
b:left()
ELSEIF ( nKey == K_HOME )
b:home()
ELSEIF ( nKey == K_END )
b:end()
ELSEIF ( nKey == K_CTRL_LEFT )
b:panLeft()
ELSEIF ( nKey == K_CTRL_RIGHT )
b:panRight()
ELSEIF ( nKey == K_CTRL_HOME )
b:panHome()
ELSEIF ( nKey == K_CTRL_END )
b:panEnd()
ELSEIF ( nKey == K_ESC )
SCROLL()
EXIT
ENDIF
END
RETURN NIL
STATIC FUNCTION Skipper( nRequest )
LOCAL nActually := 0
IF (nRequest == 0)
SKIP 0
ELSEIF (nRequest > 0) .AND. (!EOF())
WHILE (nActually < nRequest)
SKIP
IF EOF()
SKIP -1
EXIT
ENDIF
nActually++
END
ELSEIF (nRequest < 0)
WHILE (nActually > nRequest)
SKIP -1
IF BOF()
EXIT
ENDIF
nActually--
END
ENDIF
RETURN nActually
Visual FoxPro
USE test
oFormwgrid = CREATEOBJECT("MyForm")
oFormwgrid.show
READ EVENTS
DEFINE CLASS MyForm AS Form
Width=400
Height=250
ADD OBJECT b AS MyGrid
ENDDEFINE
DEFINE CLASS MyGrid AS Grid
Left=7
Top=1
Width=340
Height=240
ColumnCount=3
Column1.ControlSource='fld1'
Column2.ControlSource='fld2'
Column3.ControlSource='fld3'
Column1.Width=50
Column3.Width=200
PROCEDURE init
This.Column1.Header1.Caption='Field 1'
This.Column2.Header1.Caption='Field 2'
This.Column3.Header1.Caption='Field 3'
ENDPROC
ENDDEFINE
Clipper is an MS-DOS-based product, so you don't need to create a window
for the browse. However, because Visual FoxPro is a Windows-based product,
you need to create a window for it.
The DEFINE CLASS section creates a subclass of the Form class, and the oFormwgrid=CREATEOBJECT("MyForm") line creates an instance of that object.
Visual FoxPro
oFormwgrid=CREATEOBJECT("MyForm")
oFormwgrid.show
..
DEFINE CLASS MyForm AS Form
..
ENDDEFINE
Once you have created a window, you can add the Grid to it. Again, you will
sub-class the Grid class and create an instance of it with the ADD OBJECT b
AS MyGrid line.
Clipper
b := TBrowseDB( 3, 7, 21, 71 ) Visual FoxPro
...
ADD OBJECT b AS MyGrid
...
DEFINE CLASS MyGrid AS Grid
Left=7
Top=1
Width=340
Height=240
ColumnCount=3
...
ENDDEFINE
Now you can add columns to the Grid. Clipper creates a new column in the
Tbrowse by creating an instance of the TBColumnNew class and then passing
its handle to the addcolumn method of the Tbrowse.
In Visual FoxPro, you already set the property 'ColumnCount' to 3 in the sub-class, so you can just assign Column X's ControlSource property to the desired value. While the Grid is being initialized, you can set the titles of the column headers in the PROCEDURE init.
Clipper
column := TBColumnNew( "Field 1", {|| test->fld1 })
b:addColumn( column )
column := TBColumnNew( "Field 2", {|| test->fld2 })
b:addColumn( column )
column := TBColumnNew( "Field 3", {|| test->fld3 })
b:addColumn( column )
Visual FoxPro
Column1.ControlSource='Test.fld1'
Column2.ControlSource='Test.fld2'
Column3.ControlSource='Test.fld3'
PROCEDURE init
This.Column1.Header1.Caption='Field 1'
This.Column2.Header1.Caption='Field 2'
This.Column3.Header1.Caption='Field 3'
ENDPROC
The objects properties and methods are set in both products so you can now
give it life. Clipper does this through the stabilize method, DO .. WHILE
loops and INKEY(). Visual FoxPro ties in with the Windows event model so
you can just issue the READ EVENTS command.
Clipper
WHILE ( !b:stabilize() )
nKey := INKEY()
IF ( nKey != 0 )
EXIT
ENDIF
END
IF ( b:stable )
nKey := INKEY(0)
ENDIF
Visual FoxPro
READ EVENTSClipper/DOS is manufactured by Computer Associates, a vendor independent of Microsoft; we make no warranty, implied or otherwise, regarding this product's performance or reliability.
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Additional reference words: 3.00 VFoxWin ca clipper for dos 5.01
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