I tried everything, but everything gives me type mismatch:
Type UserType
...
End Type
Dim SomeArray() As UserType
...
If SomeArray() Is Nothing Then <do smth>
If SomeArray() Is Empty Then <do smth>
If SomeArray Is Nothing Then <do smth>
If SomeArray Is Empty Then <do smth>
I do want to know when in my array of user-defined type is no elements! Because I don't want to use additional variables if I can use VB6 possibilities.
I'll use
Erase SomeArray
when its size = 1 (UBound(SomeArray) = 1) and i want to remove last element.
WHAT I DO WRONG? XD
VB6 "Is Nothing" applies to objects, not VB6 arrays.
"Ubound(myarray)", or "Ubound - LBound" is the way to determine an array's current length in VB6.
FYI, using a VB6 Collection might be a much better for you.
Heh, I found an arse-way to solve this problem from VBForums "VB6 - Returning/Detecting Empty Arrays". B)
(L/UBound doesn't work with empty arrays - it returns out of range subscript. ;) )
So...
Private Declare Function ArrPtr Lib "msvbvm60" Alias "VarPtr" (Ptr() As Any) As Long
Private Declare Sub CopyMemory Lib "kernel32" Alias "RtlMoveMemory" (lpvDest As Any, lpvSource As Any, ByVal cbCopy As Long)
Public Function Peek(ByVal lPtr As Long) As Long
Call CopyMemory(Peek, ByVal lPtr, 4)
End Function
Remember declare your own variables BEFORE definition of this subroutines! Or it will cause some strange mistakes (VB suddenly replaced my Exit Sub statement with Exit Function!).
Then I used
If Peek(ArrPtr(SomeArray)) = 0 Then
MsgBox "Looks like empty array SomeArray() before ReDim ^_^"
End If
and
Erase SomeArray
If Peek(ArrPtr(SomeArray)) = 0 Then
MsgBox "Looks like empty array SomeArray() after Erase ^_^"
End If
and everything works fine!
Not very simple, but fine.
Thx everybody, I shall learn this chained list named Collection.
Especially thanks for VBForums, they are really geeked ones.
Related
Nim Compiler Version 1.6.6 [Windows: i386]
Compiled at 2022-05-05
Copyright (c) 2006-2021 by Andreas Rumpf
active boot switches: -d:release
Cmd Compile
nim c --cpu:i386 -d:release --app:lib --nomain mydll.nim
Hi there, I was able to return a Long value, now I'm trying to get string values.
I googled to find some exemples and find out here:
https://my.oschina.net/yuekcc/blog/775990
I'm getting this error:
VB6:
Private Declare Function MyStr Lib "mydll.dll" (ByVal s As String) As String
Private Declare Function return_multiply Lib "mydll.dll" Alias "return_multiply#8" (ByVal a As Long, ByVal b As Long) As Long
Private Sub Form_Click()
MsgBox MyStr("?") 'error
MsgBox return_multiply(5, 4) 'ok
End Sub
Another question, why the Alias has #8 at the end? return_multiply#8
Nim:
import encodings
const
vbCodePage = "GB2312"
vbTrue* = 1
vbFalse* = 0
type
VBString* = cstring
VBBoolean* = int32
proc MyStr*(): cstring {.stdcall, exportc, dynlib.} =
result = $"teste"
proc fromVBString*(a: VBString): string =
return encodings.convert($a, "UTF-8", vbCodePage)
proc toVBString*(a: string): VBString =
return VBString(encodings.convert(a, vbCodePage, "UTF-8"))
proc return_multiply*(a, b: int): int {.stdcall, exportc, dynlib.} =
a * b
Since you want to export toVBString in the dynamic library, you have to add the exportc, dynlib pragmas to it as to others:
proc toVBString*(a: string): VBString {.exportc, dynlib, stdcall.} =
return VBString(encodings.convert(a, vbCodePage, "UTF-8"))
But the definition is wrong anyway - I don't know what type VB's String is, but it certainly is different from the Nim string, and I'm not sure why you are importing it in your VB program.
Also, I don't think it's correct to just convert the Nim string to cstring to pass it to VB - Nim's cstring doesn't actually "own" the string data, so when the Nim runtime frees the Nim string, the cstring of it will point to invalid data. I don't know if VB has specific APIs for that or not though.
I know nothing about Nim, but the way to create a VB string is to make an OLE BSTR. SysAllocStringLen() would probably be your best bet. Others in that family might be better depending on what your string data looks like and where it comes from. Check out the MS docs.
I've been trying to figure out why the function below throws an error saying "Type Mismatch" when it returns. From what I know about VB6, this should work without any issue, yet it obviously does not. Can anyone see what I am doing wrong here and let me know how I can fix it? Thanks in advance.
Private Function GetByteArray(source As Variant, index As Integer, length As Integer) As Variant
Dim buff() As Byte
ReDim buff(0 To length - 1)
Dim i As Integer
For i = 0 To length - 1
buff(i) = CByte(source(index + i))
Next i
GetByteArray = buff
End Function
It turns out that the problem did not have anything to do with the Function I posted, but rather with what I was doing with the result. I was using the method to get the bytes of a double, and then using CDbl to get the double value. This is where the error was really happening.
The way I should have been doing this is to use the following code:
CopyMemory rfcTest.rfcFloat, GetByteArray(buff, 0, 8), Len(rfcTest.rfcFloat)
Note that in order to use this, you must also declare the CopyMemoryMethod like this:
Private Declare Sub CopyMemory Lib "kernel32" Alias "RtlMoveMemory" (pDest As Any, pSrc As Any, ByVal ByteLen As Long)
Using complex return type:
Public Type TimeType
hours As Integer
minutes As Integer
End Type
Public Function ParseTimeField(time As String) As TimeType
Dim timeObject As TimeType
Dim amountOfDigitHours As Integer
If time = "" Then time = "0"
If HasHoursAndMinutesParts(time) Then
amountOfDigitHours = GetAmountOfDigitHours(time)
timeObject.hours = CInt(Left(time, amountOfDigitHours))
timeObject.minutes = CInt(Right(time, 2))
Else
timeObject.hours = 0
timeObject.minutes = CInt(time)
End If
ParseTimeField = timeObject
End Function
Private Function HasHoursAndMinutesParts(time As String) As Boolean
HasHoursAndMinutesParts = Len(time) > 2
End Function
Private Function GetAmountOfDigitHours(time As String) As Integer
GetAmountOfDigitHours = Len(time) - 2
End Function
Call:
Dim timeObj As TimeType
timeObj = ParseTimeField(strTime)
OR using out parameters:
Public Function ParseTimeField(time As String, ByRef hours As Integer, ByRef minutes As Integer)
Dim timeObject As TimeType
Dim amountOfDigitHours As Integer
If time = "" Then time = "0"
If HasHoursAndMinutesParts(time) Then
amountOfDigitHours = GetAmountOfDigitHours(time)
hours = CInt(Left(time, amountOfDigitHours))
minutes = CInt(Right(time, 2))
Else
hours = 0
minutes = CInt(time)
End If
ParseTimeField = timeObject
End Function
Private Function HasHoursAndMinutesParts(time As String) As Boolean
HasHoursAndMinutesParts = Len(time) > 2
End Function
Private Function GetAmountOfDigitHours(time As String) As Integer
GetAmountOfDigitHours = Len(time) - 2
End Function
Call:
Dim hours As Integer
Dim minutes As Integer
Call ParseTimeField(strTime, hours, minutes)
BTW this is VB6 code =)
If you have a single return type, do not use an out parameter to return it.
In general, I find multiple ref/out parameters to be a code smell. If you need to return data from your method, it is better if it is in one coherent object.
I have a feeling we're going to see different opinions on this matter. Not sure there exists a best practice.
I usually prefer complex datatypes because I feel that is more in line with the original structure of functions where output parameter preceed the input parameters in the signature. Basically I don't like out parameters - they're superfluous. Whenever there's two ways of doing a thing in a programming language, you complicate unneccessary (guess I'm gonna get killed by Perl-fanatics stating this). You return data with the return statement. Period.
This said, I still find myself using out parameters often when I need to return two parameteres that have no natural grouping - i.e. would end up in a class which would be used solely in the return value of this specific function.
Whenever there's three or more parameters in the return data, I never use out simply because I find the calling code to be excessive verbose - needing to Dim the variables (or var'em in C#)
I tend to use out params as the universal style. Rarely need to implement helper functions that return UDT but these are usually private to the module so I can keep the scope of the UDT private to the module too.
In the latter case usually consume the retval like this
With ParseTimeField(strTime)
Debug.Print .hours, .minutes
End With
... and most probably would keep TimeType with private scope.
Definately a matter of opinion. I do use ByRef parameters from time to time, especially for utility functions which require a success/fail type scenario. For example, the TryParse functions in the .net framework do exactly this. Your parametrised function could look like:
Public Function ParseTimeField(time As String, ByRef hours As Integer, ByRef minutes As Integer) As Boolean
'Do stuff'
ParseTimeField = True 'or false depending on output success'
End Sub
Meaning you can call it like:
Dim hours As Integer
Dim mins as Integer
If ParseTimeField(time, hours, mins) = True Then
'It worked'
End If
However as things start to get more complicated, and you're actually returning business items as opposed to doing logical commands, then a separate class and a return type is more desirable. It also makes calling AND returning easier to maintain.
Is it possible to test a string with IsNumeric() and for it to return true, but when you cast that same string to an integer using CInt() and assign it to a variable of type integer that it will give a type mismatch error?
I ask because I was getting a type mismatch error, so I used IsNumeric() to check the string was numeric before trying to cast it, but I still get the error.
I am tearing my hair out with this.
Here is the code in question.
iGlobalMaxAlternatives = CInt(strMaxAlternatives) is where the error is occuring.
Dim strMaxAlternatives As String
Dim iGlobalMaxAlternatives As Integer
iGlobalMaxAlternatives = 0
bSurchargeIncInFare = True
strMaxAlternatives = ReadStringKeyFromRegistry("Software\TL\Connection Strings\" & sConn & "\HH", "MaxAlt")
If IsNumeric(strMaxAlternatives) And strMaxAlternatives <> "" Then
iGlobalMaxAlternatives = CInt(strMaxAlternatives)
End If
You may have an overflow due the maximum integer size; the currency type actually does very well for large numbers (but beware of any regional issues). See edits below for Int64 discussion.
According to MSDN documentation on IsNumeric:
IsNumeric returns True if the data
type of Expression is Boolean, Byte,
Decimal, Double, Integer, Long,
SByte, Short, Single, UInteger,
ULong, or UShort, or an Object that
contains one of those numeric types.
It also returns True if Expression is
a Char or String that can be
successfully converted to a number.
IsNumeric returns False if Expression
is of data type Date or of data type
Object and it does not contain a
numeric type. IsNumeric returns False
if Expression is a Char or String
that cannot be converted to a number.
Since you are getting a Type Mismatch, perhaps a Double is interfering with the conversion. The IsNumeric does not guarantee it is an Integer, just that it matches one of the numeric possibilities. If the number is a double, perhaps regional settings (comma versus period and so on) are causing the exception.
You might try converting it to a double and then to an integer.
' Using a couple of steps
Dim iValue As Integer
Dim dValue As Double
dValue = CDbl(SourceValue)
iValue = CInt(iValue)
' Or in one step (might make debugging harder)
iValue = CInt(CDbl(SourceValue))
EDIT: After your clarification, it appears you are getting an overflow conversion. First try using a Long and CLng() instead of CInt(). There is still a chance the entry is Int64 though, which is more difficult using VB6.
I have used the following code for the LARGE_INTEGER and Integer8 types (both Int64), but it may not work for your situation:
testValue = CCur((inputValue.HighPart * 2 ^ 32) + _
inputValue.LowPart) / CCur(-864000000000)
This example was from an LDAP password expiration example, but like I said it may or may not work in your scenario. If you don't have the LARGE_INTEGER type, it looks like:
Private Type LARGE_INTEGER
LowPart As Long
HighPart As Long
End Type
Search for LARGE_INTEGER and VB6 for more information.
EDIT: For debugging, it may be useful to temporarily avoid error handling and then turn it back on after passing the troubling lines:
If IsNumeric(strMaxAlternatives) And strMaxAlternatives <> "" Then
On Error Resume Next
iGlobalMaxAlternatives = CInt(strMaxAlternatives)
If Err.Number <> 0 Then
Debug.Print "Conversion Error: " & strMaxAlternatives & _
" - " & Err.Description
EndIf
On Error Goto YourPreviousErrorHandler
End If
Yes, "3.41" would be numeric but not an integer.
VB6 doesn't provide good methods to guarantee CInt won't fail. I've found the simplest way is to just use error-handling.
function TryParse(byval text as string, byref value as integer) as boolean
on error resume next
value = CInt(text)
TryParse = (err.number = 0)
endfunction
Of course your error-handling preferences may vary.
Yes. Try this:
If IsNumeric("65537") Then
Dim i As Integer
i = CInt("65537") 'throws an error on this line!
End If
This one's an overflow, but I think it illustrates the unreliability of IsNumeric() in general (especially for ints - for doubles it's much more reliable).
According to the VB6 documentation, "IsNumeric returns True if the data type of Expression is Boolean, Byte, Decimal, Double, Integer, Long, SByte, Short, Single, UInteger, ULong, or UShort, or an Object that contains one of those numeric types. It also returns True if Expression is a Char or String that can be successfully converted to a number."
Many of those cannot be converted to an Integer. For example "1.5" is numeric but it's not an integer. So, you can convert it to a number, but not necessarily an integer.
The following code works without a Type Mismatch error in Visual BASIC 6
Dim I As Integer
I = CInt("3.41")
The same for this variant
Dim I As Integer
Dim TempS As String
TempS = "3.41"
I = CInt(TempS)
Posting the code in question would help answer your question. Basically there are several function in VB6 that are used to convert strings into number.
CInt and Int convert into number but handle rounding different. Direct assignment works and equivalent to using CInt. Howver I recommend continuing to use CInt to make the operation clear to you and your fellow developers in the future.
CInt works on number with commas like "3,041.41" However VB6 has problem handling region settings so if you are using notation other than standard American English you will get strange results and errors.
Your best bet is to start logging the errors with the actual values it's working with so you can figure out whats going on.
IsNumeric will return true if it can convert the string to a number. Even if there are non-numeric characters in the string. I always loop though the string one character at a time and test each character. If one character fails then I can return an error.
Just found this nugget. If you run the following, script #1 returns TRUE but script #2 & #3 will fail:
SELECT ISNUMERIC('98,0') AS isNum -- Fails
SELECT CONVERT(INT, '98,0') -- Fails
SELECT CONVERT(NUMERIC(11,4), '98,0') -- Fails
Two options...
Change
If IsNumeric(strMaxAlternatives) And strMaxAlternatives <> "" Then
iGlobalMaxAlternatives = CInt(strMaxAlternatives)
End If
To
If IsNumeric(strMaxAlternatives) And strMaxAlternatives <> "" Then
iGlobalMaxAlternatives = CDbl(strMaxAlternatives) ' Cast to double instead'
End If
Or
If IsNumeric(strMaxAlternatives) And strMaxAlternatives <> "" Then
If CDbl(strMaxAlternatives) Mod 1 = 0 Then ' Make sure there\'s no decimal points'
iGlobalMaxAlternatives = CInt(strMaxAlternatives)
End If
End If
Need a function that takes a character as a parameter and returns true if it is a letter.
This was part of the code posted by rpetrich in response to a question by Joel Spolsky. I felt it needed a post specific to the problem it solves. It really is brilliant.
Private Function IsLetter(ByVal character As String) As Boolean
IsLetter = UCase$(character) <> LCase$(character)
End Function
You may be thinking to yourself, "Will this always work?" The documentation on the UCase and LCase functions, confirms that it will:
UCase Function Only lowercase letters are converted to uppercase;
all uppercase letters and nonletter characters remain unchanged.
LCase Function Only uppercase letters are converted to lowercase;
all lowercase letters and nonletter characters remain unchanged.
Seanyboy's IsCharAlphaA answer is close. The best method is to use the W version like so:
Private Declare Function IsCharAlphaW Lib "user32" (ByVal cChar As Integer) As Long
Public Property Get IsLetter(character As String) As Boolean
IsLetter = IsCharAlphaW(AscW(character))
End Property
Of course, this all rarely matters as all of VB6's controls are ANSI only
Private Function IsLetter(Char As String) As Boolean
IsLetter = UCase(Char) Like "[ABCDEFGHIJKLMNOPQRSTUVWXYZ]"
End Function
What's wrong with the following, which doesn't rely on obscure language behaviour?
Private Function IsLetter(ByVal ch As String) As Boolean
IsLetter = (ch >= "A" and ch <= "Z") or (ch >= "a" and ch <= "z")
End Function
I believe we can improve upon this a little more. rpetrich's code will work, but perhaps only by luck. The API call's parameter should be a TCHAR (WCHAR here actually) and not a Long. This also means no fiddling with converting to a Long or masking with &HFFFF. This by the way is Integer and adds an implicit conversion to Long here too. Perhaps he meant &HFFFF& in this case?
On top of that it might be best to explictly call the UnicoWS wrapper for this API call, for Win9X compatibility. The UnicoWS.dll may need to be deployed but at least we gain that option. Then again maybe from VB6 this is automagically redirected, I don't have Win9X installed to test it.
Option Explicit
Private Declare Function IsCharAlphaW Lib "unicows" (ByVal WChar As Integer) As Long
Private Function IsLetter(Character As String) As Boolean
IsLetter = IsCharAlphaW(AscW(Character))
End Function
Private Sub Main()
MsgBox IsLetter("^")
MsgBox IsLetter("A")
MsgBox IsLetter(ChrW$(&H34F))
MsgBox IsLetter(ChrW$(&HFEF0))
MsgBox IsLetter(ChrW$(&HFEFC))
End Sub
Looking around a bit came up with the following...
Private Declare Function IsCharAlphaA Lib "user32" Alias "IsCharAlphaA" (ByVal cChar As Byte) As Long
I believe IsCharAlphaA tests ANSI character sets and IsCharAlpha tests ASCII. I may be wrong.
Private Function IsAlpha(ByVal vChar As String) As Boolean
Const letters$ = "abcdefghijklmnopqrstuvwxyz"
If InStr(1, letters, LCase$(vChar)) > 0 Then IsAlpha = True
End Function
I use this in VBA
Function IsLettersOnly(Value As String) As Boolean
IsLettersOnly = Len(Value) > 0 And Not UCase(Value) Like "*[!A-Z]*"
End Function
It doesn't exactly document itself. And it may be slow. It's a clever hack, but that's all it is. I'd be tempted to be more obvious in my checking. Either use regex's or write a more obvious test.
public bool IsAlpha(String strToCheck)
{
Regex objAlphaPattern=new Regex("[^a-zA-Z]");
return !objAlphaPattern.IsMatch(strToCheck);
}
public bool IsCharAlpha(char chToCheck)
{
return ((chToCheck=>'a') and (chToCheck<='z')) or ((chToCheck=>'A') and (chToCheck<='Z'))
}