I'm using callbyname in vb.net to call another function with arguments. But the arguments order is only known in runtime. So I want to define the argument by it's name, not the position in the args array.
Private Sub mainSub()
Dim argArr as Object()
ReDim Preserve argArr(1)
argArr(0) = "argTwo:= "Argument Two""
argArr(1) = "argOne:= "Argument One""
callbyname(auxSub, CallType.Method, argArr)
End Sub
Private Sub auxSub(ByVal argOne as String, ByVal argTwo as String)
MsgBox("First Argument = " & argOne)
MsgBox("Second Argument = " & argTwo)
End Sub
In this example the messagebox would show the following messages:
First Argument - argTwo:= "Argument Two"
Second Argument - argOne:= "Argument One"
Instead of:
First Argument - Argument One
Second Argument - Argument Two
One possibly nasty way of doing this would be for your function to use a dictionary of argument names as the key and assign values from the argArr. If you're just using a one type of value e.g string values as in your example and the number of possible arguments is reasonably small, you could do it like the example below, but anything more complicated and as Hans said, you'd need to muck about with reflection.
Private Sub mainSub()
Dim argArr As Object()
ReDim Preserve argArr(1)
argArr(0) = "argTwo:= ""Argument Two"""
argArr(1) = "argOne:= ""Argument One"""
auxSub(argArr)
End Sub
Private Sub auxSub(argArray() As String)
'define a dictionary of arguments and add valid argument names
Dim ArgumentList As New Dictionary(Of String, String)
ArgumentList.Add("argOne", "")
ArgumentList.Add("argTwo", "")
'Iterate through the argument array and assign the appropriate value to its matching dictionary key
For Each arg As String In argArray
ArgumentList(Split(arg, " := ")(0)) = Split(arg, " := ")(1)
Next
End Sub
You would of course need more code to check that the argument names are valid of course.
Related
I would like to ask for your help regarding my problem. I want to create a module for my program where it would read .txt file, find a specific value and insert it to the text box.
As an example I have a text file called system.txt which contains single line text. The text is something like this:
[Name=John][Last Name=xxx_xxx][Address=xxxx][Age=22][Phone Number=8454845]
What i want to do is to get only the last name value "xxx_xxx" which every time can be different and insert it to my form's text box
Im totally new in programming, was looking for the other examples but couldnt find anything what would fit exactly to my situation.
Here is what i could write so far but i dont have any idea if there is any logic in my code:
Dim field As New List(Of String)
Private Sub readcrnFile()
For Each line In File.ReadAllLines(C:\test\test_1\db\update\network\system.txt)
For i = 1 To 3
If line.Contains("Last Name=" & i) Then
field.Add(line.Substring(line.IndexOf("=") + 2))
End If
Next
Next
End Sub
Im
You can get this down to a function with a single line of code:
Private Function readcrnFile(fileName As String) As IEnumerable(Of String)
Return File.ReadLines(fileName).Where(Function(line) RegEx.IsMatch(line, "[[[]Last Name=(?<LastName>[^]]+)]").Select(Function(line) RegEx.Match(line, exp).Groups("LastName").Value)
End Function
But for readability/maintainability and to avoid repeating the expression evaluation on each line I'd spread it out a bit:
Private Function readcrnFile(fileName As String) As IEnumerable(Of String)
Dim exp As New RegEx("[[[]Last Name=(?<LastName>[^]]+)]")
Return File.ReadLines(fileName).
Select(Function(line) exp.Match(line)).
Where(Function(m) m.Success).
Select(Function(m) m.Groups("LastName").Value)
End Function
See a simple example of the expression here:
https://dotnetfiddle.net/gJf3su
Dim strval As String = " [Name=John][Last Name=xxx_xxx][Address=xxxx][Age=22][Phone Number=8454845]"
Dim strline() As String = strval.Split(New String() {"[", "]"}, StringSplitOptions.RemoveEmptyEntries) _
.Where(Function(s) Not String.IsNullOrWhiteSpace(s)) _
.ToArray()
Dim lastnameArray() = strline(1).Split("=")
Dim lastname = lastnameArray(1).ToString()
Using your sample data...
I read the file and trim off the first and last bracket symbol. The small c following the the 2 strings tell the compiler that this is a Char. The braces enclosed an array of Char which is what the Trim method expects.
Next we split the file text into an array of strings with the .Split method. We need to use the overload that accepts a String. Although the docs show Split(String, StringSplitOptions), I could only get it to work with a string array with a single element. Split(String(), StringSplitOptions)
Then I looped through the string array called splits, checking for and element that starts with "Last Name=". As soon as we find it we return a substring that starts at position 10 (starts at zero).
If no match is found, an empty string is returned.
Private Function readcrnFile() As String
Dim LineInput = File.ReadAllText("system.txt").Trim({"["c, "]"c})
Dim splits = LineInput.Split({"]["}, StringSplitOptions.None)
For Each s In splits
If s.StartsWith("Last Name=") Then
Return s.Substring(10)
End If
Next
Return ""
End Function
Usage...
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
TextBox1.Text = readcrnFile()
End Sub
You can easily split that line in an array of strings using as separators the [ and ] brackets and removing any empty string from the result.
Dim input As String = "[Name=John][Last Name=xxx_xxx][Address=xxxx][Age=22][Phone Number=8454845]"
Dim parts = input.Split(New Char() {"["c, "]"c}, StringSplitOptions.RemoveEmptyEntries)
At this point you have an array of strings and you can loop over it to find the entry that starts with the last name key, when you find it you can split at the = character and get the second element of the array
For Each p As String In parts
If p.StartsWith("Last Name") Then
Dim data = p.Split("="c)
field.Add(data(1))
Exit For
End If
Next
Of course, if you are sure that the second entry in each line is the Last Name entry then you can remove the loop and go directly for the entry
Dim data = parts(1).Split("="c)
A more sophisticated way to remove the for each loop with a single line is using some of the IEnumerable extensions available in the Linq namespace.
So, for example, the loop above could be replaced with
field.Add((parts.FirstOrDefault(Function(x) x.StartsWith("Last Name"))).Split("="c)(1))
As you can see, it is a lot more obscure and probably not a good way to do it anyway because there is no check on the eventuality that if the Last Name key is missing in the input string
You should first know the difference between ReadAllLines() and ReadLines().
Then, here's an example using only two simple string manipulation functions, String.IndexOf() and String.Substring():
Sub Main(args As String())
Dim entryMarker As String = "[Last Name="
Dim closingMarker As String = "]"
Dim FileName As String = "C:\test\test_1\db\update\network\system.txt"
Dim value As String = readcrnFile(entryMarker, closingMarker, FileName)
If Not IsNothing(value) Then
Console.WriteLine("value = " & value)
Else
Console.WriteLine("Entry not found")
End If
Console.Write("Press Enter to Quit...")
Console.ReadKey()
End Sub
Private Function readcrnFile(ByVal entry As String, ByVal closingMarker As String, ByVal fileName As String) As String
Dim entryIndex As Integer
Dim closingIndex As Integer
For Each line In File.ReadLines(fileName)
entryIndex = line.IndexOf(entry) ' see if the marker is in our line
If entryIndex <> -1 Then
closingIndex = line.IndexOf(closingMarker, entryIndex + entry.Length) ' find first "]" AFTER our entry marker
If closingIndex <> -1 Then
' calculate the starting position and length of the value after the entry marker
Dim startAt As Integer = entryIndex + entry.Length
Dim length As Integer = closingIndex - startAt
Return line.Substring(startAt, length)
End If
End If
Next
Return Nothing
End Function
[Update: The question has been formed so that the functions can be copied directly into a VBA module and tested by running the test_callback_loop_function_works_with_multiple_parameters method]
I am using the Application.Run function to dynamically call methods within my VBA. The idea is that this helper will save me looping through dictionaries throughout various functions/subs within my VBA. Instead I can just call the following helper which will do the looping for me:
Public Function user_func_dictionary_loop(Dictionary As Dictionary, _
MethodCallback As String, _
Optional Params As Variant) As Boolean
Dim Key As Variant
For Each Key In Dictionary
If IsMissing(Params) Then
Application.Run MethodCallback, Dictionary(Key)
Else
Application.Run MethodCallback, user_param_replace(Dictionary(Key), Params)
End If
Next Key
End Function
If no Parameters are supplied to the function then it simply runs the MethodCallback with the Dictionary's key value. If there are parameters then an additional step is triggered below:
Private Function user_param_replace(Item As Variant, Optional Params As Variant) As Variant
Dim i As Long
Dim strTest As String
Dim Output As Variant
Output = replace_dictionary_values(Item, Params)
If IsArray(Output) Then
ReDim Preserve Output(0 To UBound(Output))
user_param_replace = Join(Output, ",")
Exit Function
End If
user_param_replace = Output
End Function
Private Function replace_dictionary_values(Item As Variant, Optional Params As Variant) As Variant
Dim l As Long
Dim varTemp() As Variant
Dim Param_Item As Variant
l = 0
If IsMissing(Params) Or Not IsArray(Params) Then
replace_dictionary_values = Replace$(Params, "{D:Value}", Item)
Exit Function
Else
ReDim varTemp(0 To UBound(Params))
For Each Param_Item In Params
varTemp(l) = Replace$(Param_Item, "{D:Value}", Item)
l = l + 1
Next Param_Item
End If
replace_dictionary_values = varTemp
End Function
The steps above allow a user to pass in parameters which contain {D:Value} which will then be replaced with the Dictionary's key value.
I've made a small unit test below with the idea that it should test the functionality of my method. At present I'm getting an "Argument not optional" error:
Function test_callback_loop_function_works_with_multiple_parameters() As Boolean
Dim dictTest As New Dictionary
dictTest.Add 1, "1 - Foo"
dictTest.Add 2, "2 - Foo"
dictTest.Add 3, "3 - Foo"
Dim MyArray(0 To 1) As Variant
MyArray(0) = "{D:Value}"
MyArray(1) = "Bar"
user_func_dictionary_loop dictTest, "custom_debug_print_multiple_params", MyArray
test_callback_loop_function_works_with_multiple_parameters = True
End Function
Function custom_debug_print_multiple_params(strPrint As String, strPrint2 As String) As String
Debug.Print strPrint & strPrint2
End Function
The output should be:
1 - FooBar
2 - FooBar
3 - FooBar
But I'm getting an
Run-time error '449' - Argument not optional
error on the Application.Run MethodCallback, user_param_replace(Dictionary(Key), Params) line.
My hunch is that because I'm trying to join array elements together with a "," to then pass through as parameters (in the Join(Output, ",") line) to the method, it's causing the test to fail.
So my question is, within VBA, is it possible to join the elements of an array together so they can then be passed, dynamically, to another method/function?
There is a problem with this line of code.
replace_dictionary_values = Replace$(Params, "{D:Value}", Item)
This line is called when IsMissing(Params) = True and, predictably, returns an error.
I also found that your test procedure can't work.
Function custom_debug_print_multiple_params(strPrint As String, strPrint2 As String) As String
Debug.Print strPrint & strPrint2
End Function
All your variables are variants but the two parameters of the above function are of string type. The arguments should be declared ByVal if variants of string type are to be passed. I recommend to test each function individually and make sure that it works before using its return value as parameters for other functions.
I suspect that part of your problem may be caused by your rather indiscriminate use of variants. For example, the Replace function you invoke in the faulty line quoted above requires 3 strings as arguments. In your code, both Item and Params (if it would exist) are variants. There is a good chance that your plan could actually work, but when something doesn't quite work, as is the case here, all those corners that were cut will have to be checked, adding more time to the debugging effort than could be saved during coding.
In the first example below the calling procedure supplies the two strings required by the called procedure. Variants of string type are passed which are converted to strings by the ByVal argument.
Function Test_TestPrint() As Boolean
Dim dictTest As New Scripting.Dictionary
Dim MyArray(0 To 1) As Variant
dictTest.Add 1, "1 - Foo"
dictTest.Add 2, "2 - Foo"
dictTest.Add 3, "3 - Foo"
MyArray(0) = "{D:Value}"
MyArray(1) = "Bar"
TestPrint MyArray(0), MyArray(1)
' user_func_dictionary_loop dictTest, "TestPrint", MyArray
Test_TestPrint = True
End Function
Sub TestPrint(ByVal strPrint As String, ByVal strPrint2 As String)
Debug.Print strPrint & strPrint2
End Sub
In the code below the array is passed to the executing procedure which expects such an array and prints out its elements.
Function Test_TestPrint2() As Boolean
Dim dictTest As New Scripting.Dictionary
Dim MyArray(0 To 1) As Variant
dictTest.Add 1, "1 - Foo"
dictTest.Add 2, "2 - Foo"
dictTest.Add 3, "3 - Foo"
MyArray(0) = "{D:Value}"
MyArray(1) = "Bar"
Sub TestPrint2 MyArray
' user_func_dictionary_loop dictTest, "TestPrint", MyArray
Test_TestPrint2 = True
End Function
I have a Sub with an array of strings as parameter:
Private Sub des(ByVal array() As String)
Dim i As Integer
For i = 0 To UBound(array)
array(i) = "hy"
Next
End Sub
When I call the function inside my main function, the value of str changes even if the array is passed to the function ByVal:
Dim str() As String
str = {"11111", "22222", "33333", "44444", "5555", "66666"}
des(str)
I tried making a copy of the array in the Sub, but it still changes in the main function.
Private Sub des(ByVal array() As String)
Dim i As Integer
Dim array2() As String
array2 = array
For i = 0 To UBound(array)
array(i) = "hy"
Next
End Sub
I read on a site that you cannot pass arrays ByVal. Is this true? If so, how should I proceed?
Try this:
Dim i As Integer
Dim array2() As String
array2 = array.Clone()
For i = 0 To UBound(array2)
array2(i) = "hy"
Next
The key difference is the .Clone(), that actually makes a shallow copy of array, and changing the values in array2 will no longer affect your str value in the main code.
Arrays are reference types. That means that when you pass an Array to your function, what is passed is always a reference, not a copy of the array. The Array in your function refers to the same array object as the Array in your calling code.
The same thing happens when you do the assign (it is not a copy!) in your second example: all you've done is make yet another reference to the same object. That is why Boeckm's solution works -- the Clone() call does make a new array and assign it values which are copies of the values in the original array.
In Visual Basic .NET, regarding arrays as parameters, there are two important rules you have to be aware of:
Arrays themselves can be passed as ByVal and ByRef.
Arrays' elements can always be modified from the function or subroutine.
You already know that you can modify the elements of an array inside a subprocess (subroutine or function), no matter how that array is defined as parameter inside that subprocess.
So, given these two subroutines:
Private Sub desval(ByVal array() As String)
array = {}
End Sub
Private Sub desref(ByRef array() As String)
array = {}
End Sub
And this very simple auxiliary subroutine (here I'll use the Console):
Private Sub printArr(ByVal array() As String)
For Each str In array
Console.WriteLine(str)
Next
End Sub
you can do these simple tests:
Dim arr1() as String = {"abc", "xyz", "asdf"}
Console.WriteLine("Original array:")
printArr(arr1)
Console.WriteLine()
Console.WriteLine("After desval:")
desval(arr1)
printArr(arr1)
Console.WriteLine()
Console.WriteLine("After desref:")
desref(arr1)
printArr(arr1)
I read on a site that you cannot pass arrays ByVal. Is this true?
No, that is not true.
An array in the .NET framework is a reference type. When you create an array, an object of System.Array will be created and its reference is assigned to the reference variable.
When you call a des method, the reference of the array object will be passed. In des method, ByVal parameter is a reference parameter variable of type System.Array, and it receive a copy of reference of an array object.
MSDN article - Passing Arguments by Value and by Reference (Visual Basic)
I have a dynamic array of strings DMAs which I declare globally.
Dim DMAs() As String
I ReDim the array and assign values to it in the CreateArrayOf function which is of type String() that returns an array of type String()
DMAs = CreateArrayOf(Sites, 2, "", False)
Public Function CreateArrayOf( _
ByRef arrayFrom() As String, _
Optional ByVal numOfChars As Integer = 2, _
Optional ByVal filterChar As String = "", _
Optional ByVal filterCharIsInteger As Boolean = False _
) As String()
Dim i As Integer, _
j As Integer, _
strn As Variant, _
switch As Boolean, _
strArray() As String
'numOfChars 2 for DMA with no filterChar
'numOfChars 3 for W with filterChar "W"
'numOfChars 3 for A with filterChar "A"
'numofChars 2 for D with filterChar "D"
ReDim strArray(LBound(arrayFrom) To LBound(arrayFrom)) 'required in order to
'not throw error on first iteration
For i = LBound(arrayFrom) To UBound(arrayFrom) 'iterate through each site
switch = False
For Each strn In strArray 'iterate through the array to find whether the
'current site already exists
If strn = Mid(arrayFrom(i), 1, numOfChars) And Not strn = "" Then
switch = True
End If
Next strn
If switch = False Then 'if it doesn't exist add it to the array
ReDim Preserve strArray(1 To UBound(strArray) + 1)
strArray(UBound(strArray) - 1) = Mid(arrayFrom(i), 1, numOfChars)
End If
Next i
CreateArrayOf = strArray 'return the new array
End Function
When I attempt to pass the DMAs array to another function OutputAnArray
Private Sub OutputAnArray(ByRef arrayToOutput() As String)
Dim i As Variant
Dim x As Integer
x = 1
For Each i In arrayToOutput
Cells(x, 6).Value = i
x = x + 1
Next i
End Sub
I get the "Type mismatch: array or user-defined type expected". Throughout the whole process I only mess with string arrays.
If I take the content of the OutputAnArray function and put it in the parent function where I'm calling it from, everything's fine.
Any help is appreciated.
I changed all String definitions to Variants
Private Sub OutputAnArray(ByRef arrayToOutput() As Variant)
The culprit was still there, so then after a whole lot of attempts to get this to compile, I removed the () from the arrayToOutput parameter and it started working.
Private Sub OutputAnArray(ByRef arrayToOutput As Variant) 'fixed
What is still perplexing is the fact that in the following function definition, the () are needed for arrayFrom.
Public Function CreateArrayOf(ByRef arrayFrom() As Variant, _ ...
I really don't get it, if anyone has any idea of an explanation, I'd love to hear it.
From the documentation:
"Arrays of any type can't be returned, but a Variant containing an array can."
If follows that the function "CreateArrayOf" does not return an array of strings: it returns a variant containing an array of strings.
The variant cannot be passed as a parameter to a function expecting an array of strings:
Private Sub OutputAnArray(ByRef arrayToOutput() As String)
It can only be passed to a function expecting a variant:
Private Sub OutputAnArray(ByRef arrayToOutput as Variant)
Conversely, DMA is an array of strings:
Dim DMAs() As String
DMA can be passed to a function expecting an array of strings:
Public Function CreateArrayOf(ByRef arrayFrom() As String, _ .
And finally, "Type mismatch: array or user-defined type expected" is a generic type mismatch message. When you pass an array of the wrong type, or a variant array, and get the error "array expected", it's not particularly helpful.
There is no problem with returning typed arrays from functions or passing typed arrays to functions as arguments. The following works as expected:
Option Explicit
Sub asdfasf()
Dim DMAs() As String
DMAs = CreateAnArray()
OutputAnArray DMAs
End Sub
Private Function CreateAnArray() As String()
Dim arr() As String
ReDim arr(1 To 5)
Dim i As Long
For i = LBound(arr) To UBound(arr)
arr(i) = i
Next
CreateAnArray = arr
End Function
Private Sub OutputAnArray(ByRef arrayToOutput() As String)
Dim i As Long
For i = LBound(arrayToOutput) To UBound(arrayToOutput)
Debug.Print arrayToOutput(i)
Next
End Sub
Now, you never show how you actually pass the DMAs array to OutputAnArray.
I'm willing to make an educated guess that you are doing
OutputAnArray (DMAs)
which will indeed result in
Type mismatch: array or user-defined type expected
You cannot freely put parentheses in that manner. They have special meaning.
If you want parentheses to be used when calling a sub, you must use Call:
Call OutputAnArray(DMAs)
And if you don't care, omit the parentheses like in the example above:
OutputAnArray DMAs
I had the same error while passing an array (of user defined type) as an argument to a function ByRef.
In my case the problem was solved using the keyword "Call" in front of the function or the sub being called.
I don't really understand it, but to me it seems like VBA is trying to interpret the function/sub a couple of different ways in the absence of "Call" - which leads to the error message.
I personally try to avoid converting anything to a variant as long as possible.
I have a Sub with an array of strings as parameter:
Private Sub des(ByVal array() As String)
Dim i As Integer
For i = 0 To UBound(array)
array(i) = "hy"
Next
End Sub
When I call the function inside my main function, the value of str changes even if the array is passed to the function ByVal:
Dim str() As String
str = {"11111", "22222", "33333", "44444", "5555", "66666"}
des(str)
I tried making a copy of the array in the Sub, but it still changes in the main function.
Private Sub des(ByVal array() As String)
Dim i As Integer
Dim array2() As String
array2 = array
For i = 0 To UBound(array)
array(i) = "hy"
Next
End Sub
I read on a site that you cannot pass arrays ByVal. Is this true? If so, how should I proceed?
Try this:
Dim i As Integer
Dim array2() As String
array2 = array.Clone()
For i = 0 To UBound(array2)
array2(i) = "hy"
Next
The key difference is the .Clone(), that actually makes a shallow copy of array, and changing the values in array2 will no longer affect your str value in the main code.
Arrays are reference types. That means that when you pass an Array to your function, what is passed is always a reference, not a copy of the array. The Array in your function refers to the same array object as the Array in your calling code.
The same thing happens when you do the assign (it is not a copy!) in your second example: all you've done is make yet another reference to the same object. That is why Boeckm's solution works -- the Clone() call does make a new array and assign it values which are copies of the values in the original array.
In Visual Basic .NET, regarding arrays as parameters, there are two important rules you have to be aware of:
Arrays themselves can be passed as ByVal and ByRef.
Arrays' elements can always be modified from the function or subroutine.
You already know that you can modify the elements of an array inside a subprocess (subroutine or function), no matter how that array is defined as parameter inside that subprocess.
So, given these two subroutines:
Private Sub desval(ByVal array() As String)
array = {}
End Sub
Private Sub desref(ByRef array() As String)
array = {}
End Sub
And this very simple auxiliary subroutine (here I'll use the Console):
Private Sub printArr(ByVal array() As String)
For Each str In array
Console.WriteLine(str)
Next
End Sub
you can do these simple tests:
Dim arr1() as String = {"abc", "xyz", "asdf"}
Console.WriteLine("Original array:")
printArr(arr1)
Console.WriteLine()
Console.WriteLine("After desval:")
desval(arr1)
printArr(arr1)
Console.WriteLine()
Console.WriteLine("After desref:")
desref(arr1)
printArr(arr1)
I read on a site that you cannot pass arrays ByVal. Is this true?
No, that is not true.
An array in the .NET framework is a reference type. When you create an array, an object of System.Array will be created and its reference is assigned to the reference variable.
When you call a des method, the reference of the array object will be passed. In des method, ByVal parameter is a reference parameter variable of type System.Array, and it receive a copy of reference of an array object.
MSDN article - Passing Arguments by Value and by Reference (Visual Basic)