LifeCycle utilities
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Tips and Tricks
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Content
Clicking a button while a loop is running
VFP 8.0+
It was asked on the UT; How can I click a botton to stop a loop process while the process is running?
If the following code is placed inside the loop, it will make the appearance that the Stop button is being clicked.
*...
lnKey = INKEY(0.01, "MH")
IF lnKey=151
loObj = SYS(1270)
IF lower(loObj.Name) = "cmdStop"
loObj.Click()
ENDIF
ENDIF
*...
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&& Check for Mouse click
&& User click the left mouse button
&& What object is the mouse over?
&& the Mouse id over the Stop button
&& Fire the click event.
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Late binding of objects
VFP 6.0+
After seeing the “My” object introduced to VFP 9.0, I decided to write a similar object for accessing many of the functions of FoxPro and windows called System.prg. In my first attempt, I encapsulated the FoxPro functions of SYS() and SET() to allow better readability. For example, Instead of the coding as SYS(3), the object version would be oSystem.UniqueName(). This helps make my coding more understandable. Well, after a while, I added other FoxPro functions like HOME, OS, VERSION, and etc. As the number of methods grew, so did the object. After a while, the time it took to instantiate the object grew also. Now recent I added methods that accessed the operating system using Win API and WMI queries. This was cool, but it was adding several seconds to the start up of my application. Something had to done to speed up the creation of the objects. The solution was not to create the individual object until they are accessed for the first time. The following snippet of code demonstrates how this is done.
loObject = CREATEOBJECT("MainClass")
? loObject.FirstObject.FirstMethod()
DEFINE CLASS MainClass as Container
FirstObject = .NULL.
PROCEDURE FirstObject_access
this.FirstObject = IIF(ISNULL(this.FirstObject), ;
CREATEOBJECT("FirstClass"), this.FirstObject)
RETURN this.FirstObject
ENDPROC
ENDDEFINE
DEFINE CLASS FirstClass as Container
PROCEDURE FirstMethod
RETURN "Hello World"
ENDPROC
ENDDEFINE
If we step through using the debugger, you will notice that after loObject is created, the property FirstObject is NULL. But when execute the second line in attempt to call FirstMethod, the FirstObject_Access method is called first, therefore creating the object for first. Then the method FirstMethod called afterwards. With several dozen obj4ects, and hundreds of methods, this means of delaying the creation of the object until they are needed speeded up the startup of the application.
You can download the latest copy of this class here
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A Read Event loop without a READ EVENTS statement.
VFP 3.0,5.0,6.0
Sometimes we need to set a form
up as the base form to a event loop, but we already have established a READ
EVENTS statement. Well DOEVENTS to the rescue. Placing a DOEVENTS in a DO WHILE
loop simulate the READ EVENTS statement. The _Exit variable controls the final
exit of the loop. The last form sets it to .T. when it closes.
DO FORM ...
...
Private _Exit
DO WHILE NOT _Exit
DOEVENTS
ENDDO
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Are your form refreshing to slow.
VFP 6.0 only
A colleague of mine purposed a problem
he was having. The problem was that on his form (entire application), when he
clicked a button or list box item, the highlighting of the selection was taking
forever. First, his form had multiple page frames, and dozens (I mean DOZENS) of
controls. I discovered that the FORM.PAINT event was being called when they were
being clicked. Therefore, I suggested, and it worked, placing a NODEFAULT in the
form's PAINT event.
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In FRX, the paths to images are saved as
absolute paths.
all versions
I have noticed that if I place
a image on a FRX report form, that when I save the report form the otherwise
relative path to the image is resolved to an absolute path. Often my clients
would like to see their logo on the header of there reports. Therefore, the
image file needs to be external to the application, where they can modify it.
But if the report form has an absolute reference to its location, it is
difficult to alter it final location (naming anywhere on the SET PATH path). The
solution I have found is to strip the path from this image reference when I
perform my automated build.
UPDATE some.FRX ;
SET PICTURE = ["]+JUSTFNAME( ALLTRIM( EVALUATE( PICTURE )))+["] ;
WHERE ObjType = 17
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All VFP versions
Contributor: Gary Vollard, Parity
Corporation.
"I have noticed on reports we have converted to VFP that
they can behave differently on various printers. During the conversion process,
we had to resize the fields to make sure that the data did not get truncated.
Okay, fine. At the time, we used an HP LJ 4 as our test printer. After all this
is said and done, we determined the field sizes for certain data types, which
helped us speed up the conversion process. Unfortunately, it turns out that
determining the field sizes did not prove to be a "universal" solution. The
converted landscape reports, when run to the Panasonic KX-P2023 printer, are
truncating the last digit of date fields. Many of our reports are very "tight"
for space, so you can't rectify the problem by merely creating a utility program
that increases field sizes in the .FRX
I called MS support, and explain the
problem. Their tech. was able to recreate the problem by creating a simple VFP
report from scratch. His conclusion was that the FoxPro report writer is
"printer specific". They will document this problem in a white paper.
To
increase your chances of success when FoxPro reports hit the field, make your
field sizes bigger than absolutely necessary. Page margins are not handled well,
either. Best bet is to implement a page margin of at least 0.20" when designing
a report, so the data won't get chopped off on the left margin."
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VFP 5.0, 6.0
The Y2K
issue is not only a problem now, but also when our application are running in
the 21 Century. For example, if a user enters a birth date of 6/10/60, the
system should assume 1960, not 2060. But if they enter a birth date for new
baby born on 6/10/01, it should assume 2001, and not 1901. VFP 5.0 and 6.0 have
a ROLLOVER clause on the SET CENTURY statement to control this, but the value
applied is the year the rollover occurs, and not the number of years into the
future it should apply. The following line resolves this oversight. It keeps
the rollover, in this case, ten (10) years beyond the current year.
#DEFINE kCentury 10
SET CENTURY TO 19 ROLLOVER MAX(0,(YEAR(DATE())+kCentury)-2000)
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VFP 5.0, 6.0
The AUSED()
function build the array of open tables and views in the reverse order they were
opened. This can be very helpful when it comes time to close all open tables.
Another example I use is closing only tables and views that were open within a
specific procedure.
PROCEDURE MyProc
LOCAL ARRAY laOpen [1,1]
=AUSED( laOpen )
...
* Perform procedure
...
LOCAL ARRAY laClose[1,1]
FOR x=1 TO AUSED( laClosed )
IF ASCAN( laOpen, laClosed[x,1])=0
USE IN (laClosed[x,1])
ENDIF
NEXT
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