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The LA Fox Developer Newsletter
August 1997
VFUG’s Hot Tips
[Ed. Note: Last month, we featured several hot tips from Fox Talk, one of several publications designed to further enhance our world. This month, we continue that trend by featuring several hot tips from VFUG, an online Visual FoxPro Developer Newsletter. For information on how to become a member and receive their newsletter, e-mail Scot Becker, Dire ctor of Marketing and Public Relations, Virtual FoxPro User Group (VFUG), scot©vfug.org. Or visit their website at http:// www.vfug.org.]

Below are some of the VFUG’s latest tips, tricks, and FAQ’s. These are so fresh, they may not even be loaded into the FAQ section by the time you read this!

Determining Affected Rows
by Sundar Raman

Ever wondered exactly how many rows were affected by that update statement that you sent to your SQL SERVER database? I ran into the problem when attempting to determine whether the change that I requested was actually committed by my request, or possibly by another user. Checking for the changes after the update with a select statement is not applicable since the change may have been committed by a different user on the network (concurrency queues). The solution that I finally found to work is to use the ROWCOUNT value that SQL Server seems to store for the connection:

cSQLString = “update tablename set fieldi = ?someval, field2 = ?someotherval where fieldi = ?oldval”
iRetVal = sqlexec(hnd, cSQLSTring) if iRetVal c 0 then
*
a connection level error happened, and is reported by the
odbc error handler endif iRetVal = sqlexec(hnd, “select @@rowcount”,
"csrTemp") if iRetVal <0 then
*
a connection level error occurred
end if select csrTemp cField = field(1)
cRowsAffected = csrTemp.&cField


NOTE: No query can be executed on the current connection between the update request, and the rowcount request. The buffer gets cleared by SQL Server every time a query is executed, and this includes things like SQLCOMM ITO, and SQLROLLBACKO.

Copying Structures
by Sundar Raman
It is very convenient to create classes to hold structures that need to be passed around a program, to different procedures and functions. The classes are always passed by reference. Every so often, it is useful to create a copy of a structure, maintaining most of the element values, but to be able to
change some of the element values temporarily. Foxpro, unfortunately, does not allow you to create a new instance of a class by direct assignment. Direct assignment creates a new pointer to the same space, or a rew reference to the same data:

obji = createobject(”myclass”) objl.propl = “poopi” obji .prop2 = “poop2” objl.prop3 = “poop3”

* trying to create a new instance, so we don’t have to explicitly copy
* all the properties over

obj2 = obji
&& this creates a new REFERENCE to the
original object obj2.propl = “poopA” && this changes BOTH obj2.propl AND objl.propl
&& of course we could always perform explicit && assignments, but who has the time for that?
obj2 = createobject(”myclass”)
obj2.prop2 = objl.prop2


To simplify this process, I wrote the following -

&& Example class definition and code

otest = createobject(”testclass”)
otesti = 0
otest.cloneobject(~otest1)
define class testclass as custombaseclass
propi =
prop2 =
prop3 = enddefine


&& Custom base class that Includes the Cloning method:
define class CustomBaseClass as custom
procedure CloneObject Iparameters toDest local oTemp, aTemp dimension aTemp(1) ?this.class
oTemp = createobject(this.class)
=amembers(aTemp, this)
if alen(aTemp) = 0 then
return
endif
for i = I to alen(aTemp)
if !sys(1269, this, aTemp(i], 1) then
*
property is read-write, so we can
set
the value
oTemp.&atemp[i] = this.&atemp[i]
endif
endfor
toDest = oTemp release oTemp release aTemp
endproc
enddefine

Moving the Print Preview Into
Your Own MDI Form
by Arnon GaI-Oz
(* How to preview reports in your own forms (instead of the
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