AL Basics of Classes in VBA with Adrian Bell

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Why use a class instead of a standard module for some of your VBA code? When you’ve seen the sorts of things you can do, and how easy it can be, you’ll answer that for yourselves. VBA Class Basics with Adrian Bell for Access Lunchtime. • Adrian said, With a simple template AccDB file, I will show some of the very basics of using classes within VBA . What the classes do is less the point than providing, and to a certain extent explaining, the bare bones of their use and how some of the basic approaches are managed. Hopefully a starting point for any interested in taking class work further. • download: • https://accessusergroups.org/lunch/ne... • 00:00 before meeting for Adrian's Basics of Classes in VBA • smile, frost blossom, raise hand • Maria, lower hands, mine's getting tired • 1:51 Introduce Adrian Bell by Maria Barnes for Basics of Classes in VBA • admin for Bytes.com, posts as NeoPa • 3:00 Adrian, Basics of Classes in VBA • 3:17 Why Use Classes? • reasons vary • powerful tools • go into basics • needn't expect to see anything overly-complicated • apply constency • mainly for illustration of concepts • 4:42 What MY database uses classes for • forms in restored view (use overlapping windows not tabbed view) • report fills up as much of the screen as possible • hide parent form after selection • reshows parent after last child has been closed • communication between objects • 6:01 demo • 6:08 simple menu: Menu A, Menu B, Menu C • 7:35 Reports menu • report class knows when last report is closed • 8:33 open 3 different reports, Ctrl+F6 = toggle • form no longer visible • when last report closed, menu form becomes visible • 9:20 Property Get • 11:28 Set is for objects and Let for scalars • 11:45 Property Let • 13:15 Property Set • 15:04 Question, New • 16:45 Access window • 16:47 menu form • 16:57 VBA code, frmMainMenu • 17:15 Private WithEvents at top • 17:49 event handlers use the internal name • 18:06 Form_Open • 20:07 choose Menu B from form • 20:24 New and WithEvents • Form_Open • 21:08 clsTo.frmFrom (parent) • 21:36 Public Function ShowForm • Initialised • Restore • open specified form • set frmChild • 22:44 strTo is the name of the form • pass extra in case there is a need • 22:33 EventPrep • 24:21 [Event Procedure] put in when you have an event handler • 24:34 Ctrl+Shift+F2 Last Position • that is what happens when you open another form • 25:36 close Menu B • set a trap in there so we get the code • 25:04 vba frmChild_Close -- from WithEvents object • 26:34 top of clsForm -- frmParent, WithEvents frmChild • 27:07 breakpoint in frmChild_Close on frmParent.Visible = True • click button, gone to that • Restore • pass name back to caller • 29:05 Public Event Closed in clsForm • 30:07 RaiseEvent statement • clsTo_Closed event handler we looked at earlier • don't have to have it, can't say that enough times • handle them if you want to, but you don't have to • 31:10 [%F] is for subtitution • 31:36 end that event handler • get back to code immediately after RaiseEvent • 32:12 back to where we started • 34:41 report - allows multiple children objects to be opened, will handle the last one is closed • how to remember which reports are open • Fixed-length string • Initialised • EventPrep • 35:26 ShowReport • code to open and handle the last one • 38:34 intIdx is an index • Instr(strInUse, vbNullChar) • is there a slot available? • 44:21 OpenReport • openend rpt03 • Secect Case intIdx • 1 and 2 set when we weren't watching • 42:36 Mid Statement • 43:30 what happens when reports close • strInUse: compare to String( conNumRpts, vnNullChar) • maybe other things happened • RaiseEvent AllClosed • ByRef -- take a different approach • 48:57 Summarize • 51:17 Ade links • 51:24 Upcoming AUG presentation on Classes • The Power of Sub Classes in VBA with Kent Gorrell for Access Pacific • https://accessusergroups.org/pacific/... • date: Thursday, 4 January 2024 • time: 6:30 pm Pacific • all are welcome, join us • 51:48 Questions, Ctrl+F6 • 54:17 here to show that one can get into classes easily • 55:00 Next for Access Pacific -- Kent • 55:27 Maria - what other examples for classes? • Neil -- Outlook listen and save data before Send • Eric -- model a domain item • tjacobi -- working with table • 58:40 perhaps Neil will do a presentation • 59:24 Question about fixed-length string • wasn't about space, like an array • 1:00:23 let things run onwards • NEXT for Lunchtime • 2024 Plans for Access by Maria Barnes • https://accessusergroups.org/lunch/ev... • date: Tuesday, 30 January 2024, noon Central time • join us! all who want to know and share about Access are welcome • Access Lunchtime • Last Tuesday • https://accessusergroups.org/lunch/

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