I need to adjust the below script to get Bitlocker status to a text file that should have the computer name as for its filename. So for a PC named Station10 the script would output a text file called Station10_enabled.txt. Or, if Bitlocker is disabled, it would create a file called Station10_disabled.txt.
I have below code, which seems to make sense, but is not working.
The code produces the error "Can not use parentheses when calling a sub", how can I fix that?
I also fear once the code runs the %computername% variable will not work or create a syntax error, but I can't test because of above issue.
If anyone out there knows how to gracefully handle what I am trying to do, please help.
strComputer = "."
Set objShell = CreateObject("Wscript.Shell")
strEnvSysDrive = objShell.ExpandEnvironmentStrings("%SystemDrive%")
Set objWMIServiceBit = GetObject("winmgmts:\\" & strComputer & "\root\CIMV2 \Security\MicrosoftVolumeEncryption")
Set colItems = objWMIServiceBit.ExecQuery("SELECT * FROM Win32_EncryptableVolume",,48)
For Each objItem in colItems
If objItem.DriveLetter = strEnvSysDrive Then
strDeviceC = objItem.DeviceID
DriveC = "Win32_EncryptableVolume.DeviceID='"&strDeviceC&"'"
Set objOutParams = objWMIServiceBit.ExecMethod(DriveC, "GetProtectionStatus")
If objOutParams.ProtectionStatus = "1" Then
My.Computer.FileSystem.WriteAllText("C:\cos\.txt","Bitlocker is enabled.",True)
Else
My.Computer.FileSystem.WriteAllText("C:\cos\test.txt","Bitlocker is disabled.",True)
End if
End If
Next
VB is a bit picky about the round brackets:
Argument lists for Function calls must be specified if you use the function result.
Argument lists for Sub calls must not be specified. The same holds true for argument lists of function calls if you do not use the function result.
The pitfall is that you usually get away if you call a sub (or function, and don´t use its result) that expects exactly one parameter, and specify that parameter in round brackets. You might believe that since this works, you may (or must) specify round brackets. This is untrue, because in that case, the round brackets can be (and are) taken as part of the expression that is evaluated to deliver the value to be passed as an actual paarmeter. That is why writing
My.Computer.FileSystem.WriteAllText("C:\cos\test.txt","Bitlocker is disabled.",True)
is syntactically invalid, while
AnyRoutineThatAcceptsOneArgument (Value)
is okay, but exactly the same as
AnyRoutineThatAcceptsOneArgument Value
If you don´t understand that, consider
AnyRoutineThatAcceptsOneArgument ((((((((Value))))))))
which is legal, but full of useless (redundant) brackets.
So the only two context where there are round brackets around routine arguments required is:
Calls to functions that expect exactly one argument, and that use the
function result.
In contrast to that, for Sub calls or function calls that don´t use the function result, you are not allowed to specify the brackets. The fact that in one special case, which is the routine call with only one argument, you are allowed to specify as many round brackets as you want has nothing to do with this. It just is an expression, and you can use as many (superfluous) brackts as you want.
Related
I'm struggling with this basic piece of code :
If Dir(LocationAddress & "\" & chart & " Complete.pdf") = "" Then
MsgBox("The file wasn't created.", vbCritical + vbRetryCancel)
Else
MsgBox ("The file was created.")
End If
When I click "save" in the VBA editor, the line corresponding to the error message turns red, and when I try to execute, it tells me there's a syntax error. I found this similar code online, with a different syntax, which also doesn't work, even when copied and pasted into the editor.
MsgBox("Important message", MsgBoxStyle.Critical, "MsgBox Example")
I also ran my initial code with only one style instruction as an optional argument, to make sure the issue wasn't simply that I was combining them with improper syntax.
I hardly know anything about vba, I've only written a few subs by copying and editing code found online.
As igittr commented above, on the line MsgBox("The file wasn't created.", vbCritical + vbRetryCancel), the parenthesis aren't needed.
When there's only one statement on the line, then VBA knows that the arguments are for the MsgBox procedure. If you put brackets around the arguments, it will try to evaluate everything within the brackets first, resulting in the error (that's why MsgBox ("The file was created.") still works, even though the brackets again aren't needed).
So either write the line as MsgBox "The file wasn't created.", vbCritical + vbRetryCancel
Or, if you want to still use brackets, use Call MsgBox("The file wasn't created.", vbCritical + vbRetryCancel). This works because you have two statements, Call and MsgBox, and the brackets are needed to indicate what procedure the arguments belong to.
Since, you show the message with some buttons option, the working solution should look as:
Dim ans As VbMsgBoxResult
ans = MsgBox("The file wasn't created.", vbCritical + vbRetryCancel, "A choice...")
If ans <> vbRetry Then Exit Sub ' the code will stop even if the right corner 'x' will be clicked.
'your code if want it continuing...
'or viceversa according to what do you intend doing in case of Cancel option.
MsgBox("The file wasn't created.", vbCritical + vbRetryCancel)
This won't work as you are calling a function as a sub. When calling functions as subs it needs to be treated as a sub which means no brackets. This is core Basic - brackets for functions and no brackets for subs.
MsgBox ("The file was created.")
This will work because you aren't using brackets for the sub. Brackets around a parameter mean pass that parameter by value. Where ever possible computer languages pass by reference as it more efficient.
However it means that the string is copied, and the copy given to msgbox. So it uses more memory.
Call
call is obsolete. In QuickBasic it allowed a different calling convention when calling inline assembler functions. Assembler didn't return a value. So the convention was to pass a variable by reference as an input parameter and on return would hold the return value.
Dir
Dir is obsolete. It became obsolete in the 90s when it was replaced by the file system object. See https://learn.microsoft.com/en-us/office/vba/language/reference/user-interface-help/filesystemobject-object
Brackets in Basic
From https://ericlippert.com/2003/09/15/what-do-you-mean-cannot-use-parentheses/
The author was the maintainer programmer at Microsoft for VBScript.
Here’s the deal: parentheses mean several different things in VB and
hence in VBScript. They mean:
Define boundaries of a subexpression: Average = (First + Last) / 2
Dereference the index of an array: Item = MyArray(Index)
Call a function or subroutine: Limit = UBound(MyArray)
Pass an argument which would normally be byref as byval: in Result
= MyFunction(Arg1, (Arg2)) , Arg1 is passed by reference, Arg2is passed by value.
That’s confusing enough already. Unfortunately, VB and hence VBScript
has some weird rules about when #3 applies. The rules are
3.1) An argument list for a function call with an assignment to the returned value must be surrounded by parens: Result = MyFunc(MyArg)
3.2) An argument list for a subroutine call (or a function call with no assignment) that uses the Call keyword must be surrounded by
parens: Call MySub(MyArg)
3.3) If 3.1 and 3.2 do not apply then the list must not be surrounded by parens.
And finally there is the byref rule: arguments are passed by reference
when possible but if there are “extra” parens around a variable then
the variable is passed by value, not by reference.
Trivia
The msgbox function is a wrapper around the Windows MessageBox() functions. Basic passes on verbatim any parameters you pass. Of course only on Windows can you use the system parameters not listed in the Basic docs. See https://learn.microsoft.com/en-us/windows/win32/api/winuser/nf-winuser-messagebox
I am learning how to create input boxes and I keep getting the same error. I have tried two different computers and have received the same error. The error I get is a "Compile Error: Wrong number of arguments or invalid property assignment"
Here is my code:
Option Explicit
Sub InputBox()
Dim ss As Worksheet
Dim Link As String
Set ss = Worksheets("ss")
Link = InputBox("give me some input")
ss.Range("A1").Value = Link
With ss
If Link <> "" Then
MsgBox Link
End If
End With
End Sub
When I run the code, it highlights the word "inputbox"
And help would be greatly appreciated.
Thanks,
G
Three things
1) Call your sub something other than the reserved word InputBox as this may confuse things. *Edit... and this alone will resolve your error. See quote from #Mat's Mug.
2) A̶p̶p̶l̶i̶c̶a̶t̶i̶o̶n̶.̶I̶n̶p̶u̶t̶B̶o̶x̶(̶"̶g̶i̶v̶e̶ ̶m̶e̶ ̶s̶o̶m̶e̶ ̶i̶n̶p̶u̶t̶"̶)̶ Use VBA.Interaction.InputBox("give me some input"). You can do this in addition to the first point. Documentation here.
3) Compare with vbNullString rather than "" . See here. Essentially, you will generally want to do this as vbNullString is, as described in that link, faster to assign and process and it takes less memory.
Sub GetInput()
Dim ss As Worksheet
Dim Link As String
Set ss = Worksheets("ss")
Link = VBA.Interaction.InputBox("give me some input")
ss.Range("A1").Value = Link
' With ss ''commented out as not sure how this was being used. It currently serves no purpose.
If Link <> vbNullString Then
MsgBox Link
End If
' End With
End Sub
EDIT: To quote #Mat's Mug:
[In the OP's code, what is actually being called is] VBA.Interaction.InputBox, but the call is shadowed by the procedure's identifier "InputBox", which is causing the error. Changing it to Application.InputBox "fixes" the problem, but doesn't invoke the same function at all. The solution is to either fully-qualify the call (i.e. VBA.Interaction.InputBox), or to rename the procedure (e.g. Sub DoSomething(), or both.
Sub InputBox()
That procedure is implicitly Public. Presumably being written in a standard module, that makes it globally scoped.
Link = InputBox("give me some input")
This means to invoke the VBA.Interaction.InputBox function, and would normally succeed. Except by naming your procedure InputBox, you've changed how VBA resolves this identifier: it no longer resolves to the global-scope VBA.Interaction.InputBox function; it resolves to your InputBox procedure, because VBAProject1.Module1.InputBox (assuming your VBA project and module name are respectively VBAProject1 and Module1) are always going to have priority over any other function defined in any other referenced type library - including the VBA standard library.
When VBA resolves member calls, it only looks at the identifier. If the parameters mismatch, it's not going to say "hmm ok then, not that one" and continue searching the global scope for more matches with a different signature - instead it blows up and says "I've found the procedure you're looking for, but I don't know what to do with these parameters".
If you change your signature to accept a String parameter, you get a recursive call:
Sub InputBox(ByVal msg As String)
That would compile and run... and soon blow up the call stack, because there's a hard limit on how deep the runtime call stack can go.
So one solution could be to properly qualify the InputBox call, so that the compiler knows exactly where to look for that member:
Link = VBA.Interaction.InputBox("give me some input")
Another solution could be to properly name your procedure so that its name starts with a verb, roughly describes what's going on, and doesn't collide with anything else in global scope:
Sub TestInputBox()
Another solution/work-around could be to use a similar function that happens to be available in the Excel object model, as QHarr suggested:
Link = Application.InputBox("give me some input")
This isn't the function you were calling before though, and that will only work in a VBA host that has an InputBox member on its Application class, whereas the VBA.Interaction.InputBox global function is defined in the VBA standard library and works in any VBA host.
A note about this:
If Link <> "" Then
This condition will be False, regardless of whether the user clicked OK or cancelled the dialog by "X-ing out". The InputBox function returns a null string pointer when it's cancelled, and an actual empty string when it's okayed with, well, an empty string input.
So if an empty string needs to be considered a valid input and you need to be able to tell it apart from a cancelled inputbox, you need to compare the string pointers:
If StrPtr(Link) <> 0 Then
This condition will only be False when the user explicitly cancelled, and will still evaluate to True if the user provided a legit empty string.
I am working on an MS Access database application that was created by someone else. There is one particular line of code (a Function) that will randomly get called and I have no idea why it is being called or what it does. I have searched (ctrl+F) the entire project for something that calls this function but I can't find it. How can I find out why this Function is being called? (See below). Thank you!
Public Function Concat(strIOSC As String, strFeature As String) As String
Static strLastIOSC As String
Static strFeatures As String
If strIOSC = strLastIOSC Then
strFeatures = strFeatures & ", " & strFeature
Else
strLastIOSC = strIOSC
strFeatures = strFeature
End If
Concat = strFeatures
End Function
If you have only searched the scripts and modules, then your scope is too narrow.
A public function like this can also be used in expressions, so you need to check queries, reports, form controls, macros, and possibly even tables if you use calculated fields. Depending on the size of the database, and how often the function is called, you can either search manually in a targeted way or possibly use a public sub to output something searchable. This sub can get you started. I think it outputs every possible location for expressions. Unfortunately, each object will have its own text file which will need to be searched separately unless you build a sub to do that too.
As for what your function does, it looks like it logs each input using the Static strLastIOSC variable, compares to the arguments passed on the second function call, and if they match it concatenates the two strFeature inputs together and outputs the result.
So basically the first argument tells the function whether this is the beginning of a new concatenation instance, or the continuation of an existing instance. The second argument is the item to be concatenated.
The Static keyword means that the value is stored even after the function runs so it can compare the last call with the current call to determine whether to add the second argument to the one saved from before, or clear the memory and prepare for a new concatenation.
Given its design, it's probably being used in a query/report/form, where strIOSC is likely a primary key field or a field in a GROUP BY.
While looking for a way to test when a user cancels an InputBox, I stumbled across the StrPtr function. I believe it checks if a variable was ever assigned a value and returns zero if it was never assigned and some cryptic number if it was.
It seems like a useful function! I started with this code:
Dim myVar as string
myVar = InputBox("Enter something.")
MsgBox StrPtr(myVar)
The message box shows a zero if the user cancelled.
Fantastic! But then why do some insist that StrPtr never be used? I read it's unsupported. Why does that matter?
A good answer will explain benefits (beyond my example above) and risks of using the StrPtr function, possibly how you use (or don't use) it without giving an opinion as to whether everyone or no one should use it.
tldr; There's no real risk to using StrPtr like that, but there's not really a benefit either.
While it might look like you get a null pointer back from the InputBox call, you actually don't. Compare the result of StrPtr to VarPtr:
Sub Test()
Dim result As String
result = InputBox("Enter something.") 'Hit cancel
Debug.Print StrPtr(result) '0
Debug.Print VarPtr(result) 'Not 0.
End Sub
That's because InputBox is returning a Variant with a sub-type of VT_BSTR. This code demonstrates (note that I've declared result as a Variant so it doesn't get implicitly cast - more on this below):
Sub OtherTest()
Dim result As Variant
result = InputBox("Enter something.") 'Hit cancel
Debug.Print StrPtr(result) '0
Debug.Print VarPtr(result) 'Not 0.
Debug.Print VarType(result) '8 (VT_BSTR)
Debug.Print TypeName(result) 'String
End Sub
The reason why StrPtr returns 0 is because the return value of InputBox is actually malformed (I consider this a bug in the implementation). A BSTR is an automation type that prefixes the actual character array with the length of the string. This avoids one problem that a C-style null terminated string presents automation - you either have to pass the length of the string as a separate parameter or the caller won't know how large to size a buffer to receive it. The problem with the return value of InputBox is that the Variant that it's wrapped in contains a null pointer in the data area. Normally, this would contain the string pointer - the caller would dereference the pointer in the data area, get the size, create a buffer for it, and then read the N bytes following the length header. By passing a null pointer in the data area, InputBox relies on the calling code to check that the data type (VT_BSTR) actually matches what is in the data area (VT_EMPTY or VT_NULL).
Checking the result as a StrPtr is actually relying on that quirk of the function. When it's called on a Variant, it returns the pointer to the underlying string stored in the data area, and it offsets itself by the length prefix to make it compatible with library functions that require a C-string. That means the StrPtr has to perform a null pointer check on the data area, because it's not returning a pointer to the start of the actual data. Also, like any other VARTYPE that stores a pointer in the data area, it has to dereference twice. The reason VarPtr actually gives you a memory address is that it gives you the raw pointer to whatever variable you pass it (with the exception of arrays, but that's not really in scope here).
So... it's really no different than using Len. Len just returns the value in the header of the BSTR (no, it doesn't count characters at all), and it also needs a null test for the similar reason that StrPtr does. It makes the logical conclusion that a null pointer has zero length - this is because vbNullstring is a null pointer:
Debug.Print StrPtr(vbNullString) '<-- 0
That said, you're relying on buggy behavior in InputBox. If Microsoft were to fix the implementation (they won't), it would break your code (which is why they won't). But in general, it's a better idea to not rely on dodgy behavior like that. Unless you're looking to treat the user hitting "Cancel" differently than the user not typing anything and hitting "Enter", there really isn't much point in using StrPtr(result) = 0 in favor of the much clearer Len(result) = 0 or result = vbNullString. I'd assert that if you need to make that distinction, you should throw together your own UserForm and explicitly handle cancellation and data validation in your own dialog.
I find the accepted answer to be rather misleading, so I was compelled to post another one.
A good answer will explain benefits (beyond my example above) and risks of using the StrPtr function, possibly how you use (or don't use) it without giving an opinion as to whether everyone or no one should use it.
There are three "hidden" functions: VarPtr, StrPtr and ObjPtr.
VarPtr is used when you need to get the address of a variable (that is, the pointer to the variable).
StrPtr is used when you need to get the address of the text data of a string (that is, the BSTR, a pointer to the first Unicode character of the string).
ObjPtr is used when you need to get the address of an object (that is, the pointer to the object).
They are hidden because it may be unsafe to mess around with pointers.
But you cannot go completely without them.
So, when do you use them?
You use them when you need to do what they do.
You use VarPtr when your problem in hand is "I need to know the address of that variable" (e.g. because you want to pass that address to CopyMemory).
You use StrPtr when your problem in hand is "I need to know the address of the first character of my BSTR string" (e.g. because you want to pass it to an API function that accepts wide strings only, but if you simply declare the parameter As String, VB will convert the string into ANSI for you, so you have to pass StrPtr).
You use ObjPtrwhen your problem in hand is "I need to know the address of that object" (e.g. because you want to examine its vtable or manually check if the object address does or does not equal some value you knew previously).
These functions correctly do what they are supposed to do, and you should not be afraid to use them for their intended purpose.
If your task in hand is different, you probably should not be using them, but not out of fear that they will return a wrong value - they will not.
In a perfect world, you would stop at that conclusion. That is not always possible, unfortunately, and the InputBox situation you mention is one of the examples.
From what is outlined above, it would appear that you should not be using StrPtr to determine if Cancel was pressed in an InputBox. Realistically though, you don't have a choice.
VBA.InputBox returns a String. (This fact is incorrectly omitted from the current documentation making it look like it returns a Variant.) It is perfectly okay to pass a string to StrPtr.
However, it is not documented that InputBox returns a null pointer on a cancel. It is merely an observation. Even though realistically that behaviour will never change, theoretically it may in a future version of Office. But that observation is all you have; there is no documented return value for a cancel.
With this in mind, you make a decision on whether or not you are comfortable with using StrPtr on the InputBox result. If you are happy to take the very small risk of this behaviour changing in future and your app therefore breaking, you do use StrPtr, otherwise you switch to Application.InputBox that returns a Variant and is documented to return a False on a cancel.
But that decision will not be based on whether StrPtr is correct in what it tells you. It is. It is always safe to pass the String result of VBA.InputBox to it.
Fantastic! But then why do some insist that StrPtr never be used? I read it's unsupported. Why does that matter?
When someone insists that something should never be used, it's almost always wrong. Even GoTo has its correct uses.
I tired both using StrPtr and without using StrPtr. I tested my Sub with several examples. I got same results except in one occasion - When User inputs null value (nothing) and presses OK.
Precisely I tried these two:
Using StrPtr. "Invalid Number" was the result here
ElseIf StrPtr(Max_hours_string) = 0
MsgBox "Cancelled"
Else
MsgBox "Invalid Number"
Without Using StrPtr. "Cancelled" was the result here
ElseIf Max_hours_string = "" Then
MsgBox "Cancelled"
Else
MsgBox "Invalid Number"
This is my code.
Sub Input_Max_Hours_From_The_User()
'Two Common Error Cases are Covered:
'1. When using InputBox, you of course have no control over whether the user enters valid input.
' You should store user input into a string, and then make sure you have the right value.
'2. If the user clicks Cancel in the inputbox, the empty string is returned.
'Since the empty string can't be implicitly coerced to a double, an error is generated.
'It is the same thing that would happen if the user entered "Haughey" in the InputBox.
Dim Max_hours_string As String, Max_hours_double As Double
Max_hours_string = InputBox("Enter Maximum hours of any Shift")
If IsNumeric(Max_hours_string) Then
Max_hours_double = CDbl(Max_hours_string) 'CDbl converts an expression to double
Range("L6").Value = Max_hours_double
Range("L6").Interior.ColorIndex = 37
ElseIf StrPtr(Max_hours_string) = 0 Then 'ElseIf Max_hours_string = "" Then MsgBox "Cancelled" also works !
MsgBox "Cancelled"
Else
MsgBox "Invalid Number"
End If
End Sub
So I think it depends how important it is to handle the null value for you. All other test cases, including pressing Cancel, non-numerical inputs etc. give the same results. Hope this helps.
Read through this thread and ultimately ended up doing the following... which does exactly what I want.... If the user deletes the previous entry which is the default... and clicks ok.. it moves forward and deletes the back end data ( not shown ). If the user click's cancel, it exists the sub without doing anything. This is the ultimate objective and... this allows it to work as intended... Move forward unless cancel is clicked.
hth,
..bob
Dim str As String
If IsNull(Me.Note) = False Then
str = Me.Note
Else
str = "Enter Note Here"
End If
Dim cd As Integer
cd = Me.ContractDetailsID
str = InputBox("Please Enter Note", "NOTE", str)
If StrPtr(str) = 0 Then
Exit Sub 'user hit cancel
End If
In my opinion: Using StrPtr in order to identify if a value converts to 0 is extra code to write. if you use the following function like your example above
Sub woohoo()
Dim myVar As String
myVar = "hello"
myVar = InputBox("Enter something.")
'if Cancel is hit myVar will = "" instead of hello.
'MsgBox StrPtr(myVar) not needed
MsgBox myVar 'will show ""
End Sub
Now is this the only reason to not use StrPtr no not at all. The other issue you run into with using unsupported functions is that eventually they can break the application. Whether its a library issue or another programmer looking through your code and trying to find that function it just is not a good idea. This may not seem like a big deal if your script is only 100 lines long. But what about when it is thousands of lines long. If you have to look at this code 2 years down the road because something broke it would not be very fun to have to find this magical function that just does not work anymore and try to figure out what it did. Lastly especially in VBA you can get overflow errors. If StrPtr is used and it goes past the allocated space of your data type that you declared it's another unnecessary error.
Just my 2 cents but due to being able to use less code and the function being more stable without it I would not use it.
10+ years Excel Programmer.
I use the Call keyword when calling subs in VB/VBA. I know it's optional, but is it better to use it or leave it off? I've always thought it was more explicit, but maybe it's just noise.
Also, I read this on another forum: Using the Call keyword is faster because it knows that it is not going to return any values, so it doesn't need to set up any stackspace to make room for the return value.
Ah ha. I have long wondered about this and even reading a two inch thick book on VBA basically says don't use it unless you want to use the Find feature of the VBE to easily find calls in large projects.
But I just found another use.
We know that it's possible to concatenate lines of code with the colon character, for example:
Function Test(mode as Boolean)
if mode = True then x = x + 1 : Exit Sub
y = y - 1
End Sub
But if you do this with procedure calls at the beginning of a line, the VBE assumes that you're referring to a label and removes any indents, aligning the line to the left margin (even though the procedure is called as intended):
Function Test()
Function1 : Function2
End Function
Using the Call statement allows concatenation of procedure calls while maintaining your code indents:
Function Test()
Call Function1 : Call Function2
End Function
If you don't use the Call statement in the above example, the VBE will assume that "Function1" is an label and left align it in the code window, even though it won't cause an error.
For VB6, if there is any chance it will be converted to VB.NET, using Call means the syntax doesn't change. (Parentheses are required in VB.NET for method calls.) (I don't personally think this is worth the bother -- any .NET converter will at least be able to put in parentheses when required. I'm just listing it as a reason.)
Otherwise it is just syntactic sugar.
Note the Call keyword is likely not to be faster when calling some other method/function because a function returns its value anyway, and VB didn't need to create a local variable to receive it, even when Call is not used.
I always use Call in VBA. To me, it just looks cleaner. But, I agree, it's just syntactic sugar, which puts it squarely the realm of personal preference. I've come across probably a dozen full time VBA guys in the past few years, and not one of them used Call. This had the added advantage that I always knew which code was mine. :p
No, it'll just add 7 characters per call with no given benefit.
No one covered this important distinction: in some (common) situations, Call prevents parentheses around function (and sub) arguments from causing the arguments to be strictly interpreted as ByVal.
The big takeaway for you is that if you DO use parentheses around arguments to a routine, perhaps by rote or habit, even though they are not required, then you SHOULD USE Call to ensure that the routine's implicit or explicit ByRef is not disregarded in favor of ByVal; or, instead, you should use an "equal sign" assignment of the return value to prevent the disregard (in which case you would not use Call).
Again, that is to protect you from unfavorably getting ByVal from a routine. Conversely, of course, if you WANT ByVal interpretation regardless of the routine's declaration, then LEAVE OFF the Call (and use parentheses).
Rationale: summarizing "ByRef and ByVal Parameters"
If
1. there is an assignment of a function call retval, e. g.
iSum = myfunc(myArg)
or
2. "Call" is used, e. g.
call myFunc(myArg)
or
call mySub(myArg)
then the parentheses strictly delineate the calling argument list; the routine declaration determines ByVal or ByRef. OTHERWISE the parentheses force ByVal to be used by the routine - even though ByVal was not specified in the routine. Thus,
mySub(myArg) 'uses ByVal regardless of the routine's declaration, whereas
Call mySub(myArg) 'uses ByRef, unless routine declares ByVal
Also note that Call syntactically mandates use of parentheses. You can go
mySub myArg
but you can't go
call mySub myArg
but you CAN go
call mySub(myArg)
(and parentheses are syntactically required for assignment of Function return value)
NOTE however that ByVal on the routine declaration overrides all of this. And FYI, ByRef is always implied in the declaration if you are silent; thus TMK ByRef has no apparent value other than documentary.
Repeating from above: The big takeaway for you is that if you DO use parentheses around arguments to a routine, perhaps by rote or habit, even though they are not required, then you SHOULD USE Call to ensure that the routine's implicit or explicit ByRef is not disregarded in favor of ByVal; or, instead, you should use an "equal sign" assignment of the return value to prevent the disregard (in which case you would not use Call).
Again, that is to protect you from unfavorably getting ByVal from a routine. Conversely, of course, if you WANT ByVal interpretation regardless of the routine's declaration, then LEAVE OFF the Call (and use parentheses).
I use Call for all VBA development of common library functions that I possibly will use in VB.NET. This allows me to move code using copy and paste between all the flavors of VB. I do this to avoid the syntax errors that the code editor creates when it "formats" or "pretty prints" the pasted code. The only edits are usually Set statement inclusion/exclusion.
If you have no plans to move your VB/VBA code to VB.NET, then there is no need to use the Call statement.
The only case I found "call" is useful is quite an accident, about some special operators.
Dim c As IAsyncOperation(Of StartupTask) = StartupTask.GetAsync("Startup")
……
(Await c).Disable()
I got a syntax error for the second line, just like what you'll get with a "New" operator. I really don't want a new variable, which is too inelegant for me. So I tried:
DirectCast(Await c, StartupTask).Disable()
This is syntactically correct. But then the IDE hinted me that the "DirectCast" is unnecessary and gave a simplification. Yes, that is:
Call (Await c).Disable()
That's why I love VS2017 Preview. 😄
If you read the MSDN Support page for the Call Statement, for the specific case o VBA, at least, it does say that Call is optional, but what is very relevant about it and nobody seems to notice is this quoted line:
"If you use either Call syntax to call any intrinsic or user-defined function, the function's return value is discarded."
This is why Call is far from useless. Say you're writing Sub SupportTasks that does a lot of very relevant stuff for you Main Subs (for example, it imports data from a file to be used by different procedures). Now, notice that since SupportTasks is reading external data, there's always a fat chance this data will not come standard and the sub will not be able to fulfill its role. What do you do?
You could, for example, use boolean functions that return False if something goes wrong. Instead of calling a sub, call a function SupportTasks inside and If statement that will exit the Main sub if there's an anomaly:
If Not SupportTasks(SomeArgument) Then
Application.ScreenUpdating = True
Exit Sub
'Else continue the Main sub regularly without writing anything in here
End If
If you're wondering what the heck this has to do with Call, consider the following: in another sub, I call SupportTasks, but I do not need its returned boolean value (for instance, I'm certain an error won't occur). Well, if I don't put it in an If statement or assign the function to a useless variable, VBA will not compile and return me an error (procedure call invalid blah blah blah must assign value to something blah blah blah). That's where Call comes in to save the day!
Call SupportTasks(SomeArgument) '<< "Call Function" call doesn't return an error
If you still think it's useless, think of it as a resource to stay organized. Writing separate procedures for routines shared by many procedures makes your code shorter and more comprehensible, specially when you're writing really large applications. ERPs built out of Excel-Access integrations, for example, can be easier to operate, repair and customize if your IT dept slow to deliver/implement the real system...
To conclude, some internet wisdom:
Always write your code as if the person who will review it is a murderous psychopath who knows where you live.
Amen.
I'm 7 years late to the party, but I just happened to come across the Call keyword a few minutes ago while reading something on MSDN. In particular, it was used to do something I thought was impossible in VB.NET (as opposed to C#) -- which is related to #FCastro's answer.
Class Test
Public Sub DoSomething()
Console.WriteLine("doing something")
End Sub
End Class
Sub Main()
Call (New Test()).DoSomething()
End Sub
In the odd case you don't need the actual object instance but require one of its methods, you can use Call to save a line. Note that this is unnecessary when it's the right-hand side of an operation:
Class Test
Public Function GetSomething() As Integer
Return 0
End Function
End Class
Sub Main()
Dim x As Integer = (New Test()).GetSomething()
End Sub