I'm struggling here a bit.
I had created a few Public variables on a form (MainForm). I now realize I need to expand the scope of some of these variable to additional forms.
So, I moved the Public declarations to a new Module called "Globals".
When I attempt to run the new form, I am getting a complaint about an ambiguous variable as I attempt to reset its value to "". No complaint from the "MainForm" using the same variables.
Module "Globals"
Public myIP As String
Public myStatus As String
New Form:
myStatus = "" << throws an err
Am I correct to move the Public variable declarations to a Module?
Any thoughts about the "ambiguous variable" err from that new Form??
Thanks!
You may be trying to declare the same variable in the same scope. See here for more details, also a SO thread related to this here.
As a side note, I notice with Excel VBA you must appropriately qualify a module-level variable if a procedure-level variable is declared with the same name.
Related
I'm stuck in VBA and I couldn't find a good answer in the other questions related to error 91. I want to create an object and store variables and arrays inside that object. I tried an approach like I would do in js:
Dim block As Object
...
Set block = Nothing
block.Name = "Unbekannter Prüfblock"
block.Awf = "Unbekannter Anwendungsfall"
block.Conditions = Array()
block.Checks = Array()
I use the "Set block = Nothing" because I will use it multiple times in a loop.
But all I get is error 91 - Object variable not set
How can I set the object?
Do I really have to declare everything in vba?
Isn't there a "stop annoying me with declaration notices" toggle? ;-)
Update
Thank you all so much for the detailed answers!
As suggested I created a class for "block" and also a class for "condition" and "check". Block for example:
Option Explicit
Public name As String
Public awf As String
Public conditions As Collection
Public checks As Collection
Then I use it inside my code like this:
Dim bl As Block
Dim co As Condition
Dim ce As Check
Set bl = New Block
bl.name = ws.Range("B" & i).value
bl.awf = ws.Range("B" & i).value
Set co = New Condition
co.attr = ws.Range("B" & i).value
co.value = ws.Range("C" & i).value
bl.conditions.Add co
VBA isn't Javascript; objects and their members cannot be created inline, they need a class definition.
When you make a member call against an object, you refer to it by name, and whenever that name refers to a null reference (Nothing) you'll get error 91.
To fix it, you need to ensure every member call is made against a valid object reference. Using the Set keyword you can assign such a reference, and to create a new instance of an object you can use the New keyword followed by the name of the class that defines the type you want a new instance of:
Dim Block As Object
Block.Something = 42 ' Error 91
Set Block = New SomeClass ' set reference
Block.Something = 42 ' OK
Note that because the object is declared As Object, every member call is late-bound (resolved at run-time); if the member doesn't exist (or if there's a typo), you'll get error 438 at run-time.
You can move this error to compile-time with early binding by using a more specific data type for the declaration:
Dim Block As SomeClass
Because the members of SomeClass are known at compile-time, the IDE will now provide you with a member completion list when you type up a member call, and typos will no longer be valid at compile-time: strive to remain in the early-bound realm whenever possible! Note: As Variant (explicit or not) is also similarly late-bound.
So we add a new class module and call it SomeClass and we add a couple of public fields:
Option Explicit
Public Name As String
Public Case As String
Public Condition As Variant
Public Check As Variant
And now you can create and consume a new instance of that class, and add instances of it to a collection to process later (note: you can't do that with a UDT/Type).
The VBIDE settings have an annoying option ("automatic syntax check", IIRC) that immediately pops a message box whenever there's a compilation error on the current line; uncheck it (invalid lines will appear in red, without a message box), but do have the "require variable declaration" setting checked: it will add Option Explicit to every module, and that will spare you from a number of easily avoidable run-time errors, moving them to compile-time.
In JS, you can add properties (together with values) on the fly to an object. That's not possible in VBA (and most other languages).
Your declaration Dim block As Object is defining a variable that is supposed to point to an Object. But it isn't pointing to anything yet, per default it is initialized with Nothing, which is, literally, nothing, and has neither properties nor methods, it's just a placeholder to signal "I don't point to anything yet". Furthermore, Object cannot be instantiated.
in VBA, you assign something to an object variable with Set (this is different to most other languages). If you want to create a new object, you use the keyword New.
However, before you do that, you need to know what kind of object (which class) you need. This can be an existing class, eg a Worksheet or a Range in Excel, or it can be an own defined class (by creating a new class module in your code). In any case, you need to define the properties and the methods of that class. Considering the most simple class module Class1 (of course you should think about a more usefull name):
Option Explicit
Public name as String
Public case as String
(I will not start to talk about private members and getter and setter).
You then write
Dim block As Class1
Set block = New Class1
block.name = "Unbekannter Prüfblock"
(But block.data = "Hello world" will not be possible as data is not a member of your class.)
Big advantage of this attempt is that the compiler can show you when you for example mistyped a property name before you even start your code (Debug->Compile). In JS, you will get either a runtime error or a new property on the fly - hard to find nasty bugs.
If you later need a new (empty) object, just create a new object using New. If the old object is not referenced anywhere else, the VBA runtime will take care that the memory is freed (so no need to write Set block = Nothing).
In case you really don't know the properties in advance (eg when you read XML or JSON files or a key-value list from an Excel sheet...), you can consider to use a Collection or a Dictionary. Plenty of examples on SO and elsewhere.
One remark to block.Condition = Array(). Arrays in VBA are not really dynamic, you cannot add or remove entries easily during runtime. In VBA, you have static and dynamic arrays:
Dim a(1 to 10) as String ' Static array with 10 members (at compile time)
Dim b() as String ' Dynamic array.
However, for dynamic members you need to define how many members you need before you write something into it, you use the ReDim statement for that. Useful if you can calculate the number of members in advance:
Redim b(1 to maxNames) ' Dynamic array, now with maxNames members (whatever maxNames is)
You can change the array size of a dynamic array with Redim Preserve, but that should be an exception (bad programming style, inperformant). Without Preserve, you will get a new array, but the former data is lost.
Redim Preserve b(1 to maxNames+10) ' Now with 10 more members.
If you really don't know the number of members and it can change often during runtime, again a Collection or a Dictionary can be the better alternative. Note that for example a Dictionary can itself a Dictionary as value, which allows to define Tree structures.
Regarding your issue adding to the collection:
You need to add this code to your class module "Block" - only then you can add objects to the collections
Private Sub Class_Initialize()
Set conditions = New Collection
set checks = new Collection
End Sub
I have a form with a variable in it called "VigilTable." This variable gets its value from the calling string OpenArgs property.
Among other things, I use this variable in the call string when opening other forms.
But it only works the first call.
MsgBox VigilTable before the call will always show "Spring2022" or whatever on the first call but always comes up blank on succeeding calls (and I get "invalid use of NULL" when the called form attempts to extract the value from OpenArgs). The variable is dimmed as String in the General section of the form's VBA code.
So what's happening here? And can I fix it?
Thanks.
Ok, so you delcared a variable at the form level (code module) for that given form.
and we assume that say on form load, you set this varible to the OpenArgs of the form on form load.
So, say like this:
Option Compare Database
Option Explicit
Public MyTest As String
Private Sub Form_Load()
MyTest = Me.OpenArgs
End Sub
Well, I can't say having a variable helps all that much, since any and all code in that form can use me.OpenArgs.
but, do keep in mind the following:
ONLY VBA code in the form can freely use that variable. It is NOT global to the applcation, but only code in the given form.
However, other VBA code outside of the form can in fact use this variable. But ONLY as long as the form is open.
So, in the forms code, you can go;
MsgBox MyTest
But, for VBA outside of the form, then you can get use of the value like this:
Msgbox forms!cityTest.MyTest
However, do keep in mind that any un-handled error will (and does) blow out all global and local variables. So, maybe you have a un-handled error.
Of course if you compile (and deploy) a compiled accDB->accDE, then any errors does NOT re-set these local and global variables.
but, for the most part, that "value" should persist ONLY as long as the form is open, and if you close that form, then of course the values and variables for that form will go out of scope (not exist).
Now, you could consider moving the variable declare to a standard code module, and then it would be really global in nature, but for the most part, such code is not recommended, since it hard to debug, and such code is not very modular, or even easy to maintain over time.
So, this suggests that some error in VBA code is occurring, and when that does occur, then all such variables are re-set (but, the noted exception is if you compile down to an accDE - and any and all variables will thus persist - and even persist their values when VBA errors are encountered.
For a string variable, a more robust solution not influenced by any error, should be writing/reading in/from Registry. You can use the, let as say, variable (the string from Registry) from any workbook/application able to read Registry.
Declare some Public constants on top of a standard module (in the declarations area):
Public Const MyApp As String = "ExcelVar"
Public Const Sett As String = "Settings"
Public Const VigilTable As String = "VT"
Then, save the variable value from any module/form:
SaveSetting MyApp, Sett, VigilTable , "Spring2022" 'Save the string in Regisgtry
It can be read in the next way:
Dim myVal as String
myVal = GetSetting(MyApp, Sett, VigilTable , "No value") 'read the Registry
If myVal = "No value" Then MsgBox "Nothing recorded in Registry, yet": Exit Sub
Debug.print myVal
Actually, this proved not to be the the answer at all.
It was suggested that I declare my variables as constants in the Standard module but I declared them as variables. It appeared at first to work, at least through one entire session, then it ceased to work and I don't know why.
If I declare as constants instead, will I still be able to change them at-will? That matters because I re-use them with different values at different times.
I didn't do constants but declaring VigilName in the Standard module and deleting all other declarations of it fixed both problems.
While I was at it I declared several other variables that are as generally used and deleted all other declarations of them as well so that at least they'll be consistently used throughout (probably save me some troubleshooting later.
Thanks to all!
In a userform, I have this at the top:
Public DelMonth As Variant
The value of DelMonth is read from a ComboBox, and I can call it from different subroutines within that userform just fine. But when I call it from a separate module, it doesn't read it. It doesn't even throw an error. If I do a MsgBox DelMonth, it doesn't do anything.
A form is an object; a public field in an object module belongs to an instance of that object. UserForms are little more than class modules with a default instance (i.e. a VB_PredeclaredId = True attribute) and a designer.
If you're using the form's default instance (a rather bad idea), then you can do this:
MsgBox UserForm1.DelMonth
Note that storing state in global objects is bug-prone, and will end up causing issues.
If you're treating the form like the full-fledged class it is, then you'll have something like this:
With New UserForm1
.Show
MsgBox .DelMonth
End With
Note that the field being Public means anyone, anywhere can go and write to it. What you mean is for the form to determine its value, and for the caller to be able to read that value. You do this by encapsulating the field with a Property Get member - start by making the field Private:
Option Explicit
Private DelMonth As Variant ' wouldn't Integer or Long be more appropriate?
Public Property Get DeliveryMonth() As Long
DeliveryMonth = DelMonth
End Property
Now the callers don't get to see the private DelMonth, and all they can do with DeliveryMonth is call the Get accessor, which doesn't let them tamper with the encapsulated value.
It doesn't even throw an error.
That's worrying. You're allowing VBA to happily compile typos and otherwise illegal code. Specify Option Explicit at the top of every module. Always.
In VBA for Access, how do I make a global variable that I can access and change anywhere?
You can declare a variable at Global scope by declaring it in a Standard Module or a predeclared class module such as a Worksheet, UserForm or PreDeclared class, using the Public keyword:
Public myVar As String
You can also declare a Global variable using the now deprecated, but still valid Global syntax, which is functionally the same as Public
Global myVar As String
But note that declaring a variable with Public or Global will make the variable accessible across your entire project AND to any project that refers to that project, and even if your project is protected, a user could still query the variable from the Immediate window.
If you must have a variable that is available across your project, but only that project, then you should declare the variable in a standard module, and include an Option Private Module statement to make the module private to the project, but its variables as Public to the project only.
Option Private Module
Public myVar As String
I am trying to call a public subroutine from a Windows form based on a string variable containing the name of the subroutine. The subroutine is a procedure in a code module and works fine when called by using the procedure name directly.
The VB.net function CallByName should work, but I don't know how to specify the module name as the "Object Ref" parameter.
In the code shown, "ReportLibrary" is a module containing the public sub with the name contained in the string strReportProcedure. This results in the following error helper:
The Help says this about the ObjectRef parameter:
ObjectRef
Type: System.Object
Required. Object. A pointer to the object exposing the property or method.
What am I missing or is it just not possible to call a routine from a module using CallByName?
CallByName will not work for code in VB.Net modules since the first parameter requires an object. You need to move the methods into a class, then create an instance of the class in order to make CallByName work.
Hmmm, I think the problem is somewhere else.
I think you haven't declared a variable like this:
Dim RL as NEW Reportlibrary
And after declaring it, use this:
CallByName(RL, strReportProcedure , CallType.Method , blnPreview)
Probably the problem was in declaration, because (in your case) your class doesn't let you access to your library's subroutines. That's why you need to declare "as New ReportLibrary".
Good Luck !
Dim object As NEW Reportlibrary and then just use that Object.