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tmrRefresh object: ThisForm.Refresh This.Enabled = .F. To help make the point clearer, the following is the code for the cmdNext CommandButton: ThisForm.ors.MoveNext Did you notice that a call to the Refresh method of the form isn’t present in the CommandButton? The same is true for the other navigation buttons as well. What does this mean? It means that code only has to exist in one location. The alternative is to have method calls in multiple locations. Since the COM events aren’t surfaced in VFP, this is usually a required course of action. With the ability to both recognize events and attach VFP code to those events, refresh code only has to be written once and, most importantly, only called from one location: the MoveComplete event. What’s the benefit? Whether you navigate via a CommandButton or the DataGrid control, the MoveComplete event will fire. The form will refresh. Clearly, this is a much better design—especially from a code maintenance standpoint. At this point, you might be asking, why the Timer Control? I had problems calling the Refresh method directly in the event. To avoid errors and get the correct functionality, the Refresh method had to be called after the MoveComplete event fired. At this point, I don’t know what’s causing the problem. I’ll be reporting this to the VFP team at Microsoft and will report back on their response. A quick word on the _VFP AutoYield property By default, the AutoYield property of the _VFP object is set to .T. This means that VFP will automatically process pending Windows events that occur between the execution of VFP program code. For this solution to work properly, you must be sure that the AutoYield Property is set to .F. Otherwise, the events will never be surfaced in VFP. This task is taken care of in the Load event of the form. The AutoYield setting is reset to the default in the Destroy event. Conclusion Once again, the joining of VFP, Visual Basic, and ADO can prove to be a powerful combination. Using a Visual Basic-created ActiveX control provides a way to bring functionality that doesn’t exist in VFP. For this reason, it’s more important than ever to go beyond VFP and give serious consideration to the other tools Visual Studio has to offer. Language aside, this article brings to light issues to ponder when considering a design. Clearly, when possible, make use of events to centralize code—as opposed to making redundant method calls. From a maintenance standpoint, you’ll definitely save yourself Figure 4. The live VFP form implementing the two ActiveX controls. a lot of work. Finally, I want to take this opportunity to thank my writing partner and friend Rod Paddock for being a great sounding board for this article. This is definitely new and uncharted territory. Rod’s assistance was invaluable when I needed to negotiate the rough spots. ▲ 12PETERS.ZIP at www.pinpub.com/foxtalk John V. Petersen, MBA, is vice president of IDT Marketing Systems and Services, a Philadelphia-based marketing database consulting firm. John has presented at numerous developer conferences, including DevCon 97, Tech-Ed, and the Southwest Visual FoxPro Conference. John is a Microsoft Most Valuable Professional (MVP) and a co-author of Developing Visual FoxPro 5.0 Enterprise Applications and Hands-On Visual Basic 5—Web Development, both from Prima Publishing. j_petersen@idtmarketing.com. 18 FoxTalk December 1998 http://www.pinpub.com
Second Star on the Right and Straight on ’til Morning Paul Maskens and Andy Kramek This month, Paul and Andy take a look at naming and object referencing. Paul: I was reading through threads on CompuServe recently and picked up a few ideas from there, things that seem to be causing people trouble, that we can deal with here. There appears to be a general confusion about where to put the code in a VFP application and how to refer to the user interface controls in that code. The power and flexibility of VFP doesn’t help either, as there’s no one right way to do things. Andy: Let’s start with naming and referencing in this column. We’ll worry about where to put the code next time. The first thing is to give things meaningful names. Imagine a form with 25 text boxes named Text1 to Text30 randomly (with some numbers missing, of course). Paul: I don’t have to imagine it, I’ve seen it! Not only that, but every form in the application had a Name of “Form1,” which didn’t make life any easier. Andy: So here’s a guideline for you, then. Name your forms with the same name as their SCX (that has to be unique within the application anyway), and add to your basic form class a Label named lblFormName that has in its INIT() method THIS.caption = THISFORM.Name. Now whenever you run your form, you have a little label showing the actual name of the form, and when the user encounters an error, he or she can tell you which form the error was in, with a name that means something to you. Paul: You’re presuming that we use a form class, of course. (We ought to return to that point some time, too.) For now, can we just assume things are simple? Even using VFP base classes, as many beginners do. For example, take a form with a text box and a Command button. We’re obviously agreed that the first thing is to give them names so you can refer to them. Accepting the VFP default of Form1, Text1, and Command1 isn’t going to be very helpful in the long term! So once they have names like frmCustomer, txtName, and cmdSearch, the function of this form and the controls on it begin to be self-explanatory. The Kit Box FoxTalk Andy: I would emphasize that using names isn’t a substitute for adding comments, no matter how clear those names are! http://www.pinpub.com FoxTalk December 1998 19 6.0 Paul: Yes! There’s a much under-used form property named Comment in the VFP base class. Like the Tag property, this property is never addressed directly by VFP itself. It’s entirely for developer use. Typically, Comment is for, well, comments, and Tag is for data. I want to keep this simple, so let’s have the button change the background color of the text box. Now we have a form named frmDemo. No, er, it’s the first demo of many. So let’s try frmDemo1. Whoops, we’re back to the Text1-Text30 problem described earlier. Uh, how about frmColourChangingDemo? Andy: See, naming things is harder than writing the code! Just call it frmColChg—that means we don’t need to argue about how to spell “color.” Paul: Okay, so following on from that, we could have cmdChgCol to change the color, and txtShoCol that shows the color change. The code is really easy now. In the Click() event of cmdChgCol, it’s just one line of code: THISFORM.txtShoCol.backcolor = RGB(255,0,0). Andy: That’s fine. It’s an example of indirect referencing that will work as long as both objects are on the form. Now how about making this very useful tool reusable by creating a class and putting the class on the form instead of the individual controls. Just select both of the controls and choose Save As Class from the File menu. Name the class and the library to store it in. Then delete the controls and add an instance of the new class to the form. Paul: What about the name of this new class? And what’s the name of this class’s instance on the form? I reckon cntChgCol is pretty good for the class, and to make matters a little confusing, I think it’s a good name for the instance, too. Oh! Once I did that, everything fell apart, though. Running the form produces an “<strong>Un</strong>known member ‘txtShoCol’ (Error 1925)”. I know it’s there—I can see it, and its name is still txtShoCol in the form designer. But
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Page 3 and 4: Bug Fixes Available at microsoft.co
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Page 15 and 16: ActiveX and Automation Review FoxTa
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Un-Mapping Mapped Network Drives Andrew Coates - dFPUG-Portal

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