Un-Mapping Mapped Network Drives Andrew Coates - dFPUG-Portal

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you do to ensure that I don’t get lost when I’m coming to your new offices for the very first time? Paul: Easy, draw you a map! Andy: Give the man a cigar! So why don’t we apply this solution to this case? Figure 2 shows a map of the object hierarchy for the form shown previously. Paul: That’s pretty neat. It’s just a standard Organization Chart, isn’t it? It looks rather like the Object model diagrams that MS produces for what used to be OLE Automation (I can’t remember what it’s called this week). Andy: Yes, it was produced using the MS Organization Chart 2.0 add-on that ships with Office, and you can use it to work out how to reference things correctly. All you need to do is start “walking” from the initial object (“This”) toward the object you want to address. Each time you meet a shaded object, you must add that to the address—using “Parent” if you’re climbing up the tree, and the object’s name if you’re going down. Paul: Okay—let’s suppose I want the Save button to read the person’s “Known As” name. I start from the button with ‘This’, then move upwards and find myself at the cntFormMode object, which is shaded, so I add a parent reference to get ‘This.Parent’. Carrying on upwards, I reach the form object (also shaded, so I need another “parent”) and get ‘This.Parent.Parent’ before starting downwards again to arrive at cntName—which just gets added: ‘This.Parent.Parent.cntName’. Finally, I reach the target text box, so my full address (for the Value property) is ‘This.Parent.Parent.cntName .txtKnownAs.Value’. Figure 2. Object hierarchy diagram. Andy: Correct. Of course, you can also take a shortcut, since you can see from the object hierarchy that you have to get all the way up to the form before you can start downwards again toward your objective. So you can simply start directly from the form using “ThisForm”, which would give you the address ‘ThisForm.cntName .txtKnownAs.Value’. Figure 3. Improved object hierarchy diagram. Paul: There’s one thing your diagram doesn’t make clear—why can’t I go directly from cntFormMode to cntName without passing through the form? There’s a line between them, isn’t there? Andy: No, there isn’t. Remember, we’re dealing with a hierarchy, so you can only go up or down. In reality, there’s no direct connection between the two containers— it’s just drawn that way for simplicity. Each object in the top row is actually connected directly, and only, to the form. “All roads lead to Form” . Similarly, to get from one text box in a container to another in the same container, you must go up to the container level before starting back down again. I suppose a more correct representation of the situation would look like Figure 3 (I’ve added a few other objects so that you can see how they fit). Paul: Yes, that’s quite clear now. I do things slightly differently. Because I don’t always work these things out in advance, what I often do is print out the form and then 22 FoxTalk December 1998 http://www.pinpub.com
write on it. I keep printouts of the form anyway for documentation, so an extra one for my reference is no great effort. While I’m in the form designer, I just press PrtSc on the keyboard, Alt-Tab to paintbrush, and Ctrl-V to paste in the screenshot, then print it landscape. Then I get out the four colored pens and draw boxes around the containers, write in their names, and write the names of controls. Then I might even write in the names of methods too, because there are occasions when the interface design is done with the customer before the rest of the design is finalized. Andy: That’s a useful little technique; I’d better try that out. Doing it in the designer means that you’ll get the names of all but the very smallest objects as part of the printout, too—nice! (I’ve always done it using a proprietary screen capture tool with the form running; I think I forgot about the PrtSc key when I gave up DOS). Paul: So do you want to summarize this whole business neatly now? Andy: I think so; let’s see. When Wendy Darling asked Peter Pan how to get to Never-Never Land, he drew her a mental map and used names that meant something to her. We need to follow the same approach when working with forms and containers. Name the objects meaningfully, and use some sort of visualization of the entire object hierarchy to ensure that we address objects properly. Doesn’t seem too difficult, really, does it? Paul: Nope, not difficult at all. One small difference, though—in FoxPro, if you don’t have a map, your program ends up in Never-Never Land. While you’re there, if you see a bag of marbles about, they’re mine! (clap, clap, clap, clap, clap, I do believe in FoxPro!) ▲ Paul Maskens is a VFP specialist and FoxPro MVP who works as systems engineer for AZURE IT Ltd., based in Oxford, England. pmaskens@compuserve.com. Andy Kramek is an old FoxPro developer and FoxPro MVP who works as an independent contractor based in Birmingham, England. andykr@solihull.bytenet.co.uk. Downloads December Subscriber Downloads • 12COASC2.ZIP—Source code described in Andrew Coates’s article, “Un-Mapping Mapped Network Drives.” • 12DONNSC.ZIP—Source code described in Jefferey Donnici’s article, “Seeing Patterns: The Mediator.” • 12DHENSC.ZIP—Source code described in Doug Hennig’s article, “Mining for Gold in the FFC.” • 12PETERS.ZIP—Source code described in John Petersen’s article, “Integrating ADO and Visual Basic into Your VFP Applications, Part 2.” Extended Articles • 12SETTI.HTM—Stephen Settimi’s article, “Creating a Set of Business Rules and the Making of a BusinessRule Server.” In this article, Stephen first shows how to visualize a business object as a collection of smaller objects. Once the objects are clearly identified and defined (the latter isn’t covered in Earn Money! . . . and see your name in print this article), it’s time to set out those business objects that might need rules, define those rules, collect them, and then execute them through a BusinessRule Server and maintain them as discrete object components. • 12SETTI.ZIP—Source code described in Stephen Settimi’s article, “Creating a Set of Business Rules and the Making of a BusinessRule Server.” • 12BOOTH.HTM—Jim Booth’s article, “What’s Really Inside: To Open the Tables or Not to Open the Tables—That is the Question.” Have you ever wondered if there’s any benefit to opening the tables for a SQL SELECT command before you execute the SELECT? Does the SELECT use the source tables that are already open? Interesting questions. Here are the answers. • 12BERG.HTM—“To PrintScreen or Not to PrintScreen.” Art Bergquist’s follow-up to his September article, “The Visual FoxPro Screen Image Printer.” Go ahead, add a line to your résumé—“Published Articles.” If your tip shows up in the pages of FoxTalk, we’ll send you $25. See the back page for the address where you can send your tips. http://www.pinpub.com FoxTalk December 1998 23
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Un-Mapping Mapped Network Drives Andrew Coates - dFPUG-Portal

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