Return multiple values from a function, sub or typ

问题:

So I was wondering, how can I return multiple values from a function, sub or type in VBA? I've got this main sub which is supposed to collect data from several functions, but a function can only return one value it seems. So how can I return multiple ones to a sub?

回答1:

You might want want to rethink the structure of you application, if you really, really want one method to return multiple values.

Either break things apart, so distinct methods return distinct values, or figure out a logical grouping and build an object to hold that data that can in turn be returned.

' this is the VB6/VBA equivalent of a struct
' data, no methods
Private Type settings
    root As String
    path As String
    name_first As String
    name_last As String
    overwrite_prompt As Boolean
End Type


Public Sub Main()

    Dim mySettings As settings
    mySettings = getSettings()


End Sub

' if you want this to be public, you're better off with a class instead of a User-Defined-Type (UDT)
Private Function getSettings() As settings

    Dim sets As settings

    With sets ' retrieve values here
        .root = "foo"
        .path = "bar"
        .name_first = "Don"
        .name_last = "Knuth"
        .overwrite_prompt = False
    End With

    ' return a single struct, vb6/vba-style
    getSettings = sets

End Function

回答2:

You could try returning a VBA Collection.

As long as you dealing with pair values, like "Version=1.31", you could store the identifier as a key ("Version") and the actual value (1.31) as the item itself.

Dim c As New Collection
Dim item as Variant
Dim key as String
key = "Version"
item = 1.31
c.Add item, key
'Then return c

Accessing the values after that it's a breeze:

c.Item("Version") 'Returns 1.31
or
c("Version") '.Item is the default member

Does it make sense?

回答3:

Ideas :

1. Use pass by reference (ByRef)
2. Build a User Defined Type to hold the stuff you want to return, and return that.
3. Similar to 2 - build a class to represent the information returned, and return objects of that class...

回答4:

You can also use a variant array as the return result to return a sequence of arbitrary values:

Function f(i As Integer, s As String) As Variant()
    f = Array(i + 1, "ate my " + s, Array(1#, 2#, 3#))
End Function

Sub test()
    result = f(2, "hat")
    i1 = result(0)
    s1 = result(1)
    a1 = result(2)
End Sub

Ugly and bug prone because your caller needs to know what's being returned to use the result, but occasionally useful nonetheless.

回答5:

A function returns one value, but it can "output" any number of values. A sample code:

Function Test (ByVal Input1 As Integer, ByVal Input2 As Integer, _
ByRef Output1 As Integer, ByRef Output2 As Integer) As Integer

  Output1 = Input1 + Input2
  Output2 = Input1 - Input2
  Test = Output1 + Output2

End Function

Sub Test2()

  Dim Ret As Integer, Input1 As Integer, Input2 As Integer, _
  Output1 As integer, Output2 As Integer
  Input1 = 1
  Input2 = 2
  Ret = Test(Input1, Input2, Output1, Output2)
  Sheet1.Range("A1") = Ret     ' 2
  Sheet1.Range("A2") = Output1 ' 3
  Sheet1.Range("A3") = Output2 '-1

End Sub

回答6:

you can return 2 or more values to a function in VBA or any other visual basic stuff but you need to use the pointer method called Byref. See my example below. I will make a function to add and subtract 2 values say 5,6

sub Macro1
    ' now you call the function this way
    dim o1 as integer, o2 as integer
    AddSubtract 5, 6, o1, o2
    msgbox o2
    msgbox o1
end sub


function AddSubtract(a as integer, b as integer, ByRef sum as integer, ByRef dif as integer)
    sum = a + b
    dif = b - 1
end function

回答7:

Not elegant, but if you don't use your method overlappingly you can also use global variables, defined by the Public statement at the beginning of your code, before the Subs. You have to be cautious though, once you change a public value, it will be held throughout your code in all Subs and Functions.

回答8:

I always approach returning more than one result from a function by always returning an ArrayList. By using an ArrayList I can return only one item, consisting of many multiple values, mixing between Strings and Integers.

Once I have the ArrayList returned in my main sub, I simply use ArrayList.Item(i).ToString where i is the index of the value I want to return from the ArrayList

An example:

 Public Function Set_Database_Path()
        Dim Result As ArrayList = New ArrayList
        Dim fd As OpenFileDialog = New OpenFileDialog()


        fd.Title = "Open File Dialog"
        fd.InitialDirectory = "C:\"
        fd.RestoreDirectory = True
        fd.Filter = "All files (*.*)|*.*|All files (*.*)|*.*"
        fd.FilterIndex = 2
        fd.Multiselect = False


        If fd.ShowDialog() = DialogResult.OK Then

            Dim Database_Location = Path.GetFullPath(fd.FileName)

            Dim Database_Connection_Var = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source=""" & Database_Location & """"

            Result.Add(Database_Connection_Var)
            Result.Add(Database_Location)

            Return (Result)

        Else

            Return (Nothing)

        End If
    End Function

And then call the Function like this:

Private Sub Main_Load()
  Dim PathArray As ArrayList

            PathArray = Set_Database_Path()
            My.Settings.Database_Connection_String = PathArray.Item(0).ToString
            My.Settings.FilePath = PathArray.Item(1).ToString
            My.Settings.Save()
End Sub

回答9:

you could connect all the data you need from the file to a single string, and in the excel sheet seperate it with text to column. here is an example i did for same issue, enjoy:

Sub CP()
Dim ToolFile As String

Cells(3, 2).Select

For i = 0 To 5
    r = ActiveCell.Row
    ToolFile = Cells(r, 7).Value
    On Error Resume Next
    ActiveCell.Value = CP_getdatta(ToolFile)

    'seperate data by "-"
    Selection.TextToColumns Destination:=Range("C3"), DataType:=xlDelimited, _
        TextQualifier:=xlDoubleQuote, ConsecutiveDelimiter:=False, Tab:=True, _
        Semicolon:=False, Comma:=False, Space:=False, Other:=True, OtherChar _
        :="-", FieldInfo:=Array(Array(1, 1), Array(2, 1)), TrailingMinusNumbers:=True

Cells(r + 1, 2).Select
Next


End Sub

Function CP_getdatta(ToolFile As String) As String
    Workbooks.Open Filename:=ToolFile, UpdateLinks:=False, ReadOnly:=True

    Range("A56000").Select
    Selection.End(xlUp).Select
    x = CStr(ActiveCell.Value)
    ActiveCell.Offset(0, 20).Select
    Selection.End(xlToLeft).Select
    While IsNumeric(ActiveCell.Value) = False
        ActiveCell.Offset(0, -1).Select
    Wend
    ' combine data to 1 string
    CP_getdatta = CStr(x & "-" & ActiveCell.Value)
    ActiveWindow.Close False

End Function