getting a variable to point at another... byref

[ThatRickGuy]

Hey guys, I'm having a brain fart this afternoon.

I have a method that takes a parameter byRef. I need to use that variable, and modify it, and I want to sender to see the same changes. The problem is I need to use the variable out side of the scope of that specific method.

here's a short version:

class MyClass
  private _MyVar as string

  public sub New(byRef MyVar as string)
    [b]_MyVar = MyVar[/b]
  end sub

  Public sub SomethingElse()
    _MyVar &= "SomethingElse"
  End sub
end class

The bolded line is, as expected copying the value that MyVar contained when it was passed in. But I want _MyVar to point at the same object in memory. And for the life of me, I can't remember how.

-Rick

VB.Net Forum forum796 forum855 ASP.NET Forum
I believe in killer coding ninja monkeys.

 

[SiriusBlackOp]

I'm confused too... LOL!

Can you use this?: IReferenceService.GetReference

Senior Software Developer

http://www.scoutsft.com

 

[chrissie1]

I think that won't work with a string try doing it with an object. Wait I'll try that.



Christiaan Baes
Belgium

My Blog
"In a system where you can define a factor as part of a third factor, you need another layer to check the main layer in case the second layer is not the base unit." - jrbarnett

 

[ThatRickGuy]

Unfortunately, no. At least, not with out going through a good bit of extra work...

The object that is getting passed around is an object that stores credential info for database logins. The first time I pass the credentials into the DAL it is nothing. The DAL instantiates and populates it, and stores it local to that object, but I wanted to keep a reference to that single credentials object. so that back at the calling code, after the first DAL call is completed, the variable that I passed in would then be a populated credentials object.

I have a workaround in place, I just pull the value out manually on the next line via a property. But it would have been cleaner to do it via the byRef parameter.

-Rick

VB.Net Forum forum796 forum855 ASP.NET Forum
I believe in killer coding ninja monkeys.

 

[chrissie1]

actually I was right

Public Class Class2
    Private _s As String

    Public Property S() As String
        Get
            Return _s
        End Get
        Set(ByVal value As String)
            _s = value
        End Set
    End Property
End Class

I created an extra class as above and used that and then it works. I think it has something to witht the fact that strings are immutable.

And then this

Dim p As New Class2
        p.S = "first"
        Me.TextBox1.AppendText(p.S & ControlChars.CrLf)
        Dim s As New Class1(p)
        Me.TextBox1.AppendText(p.S & ControlChars.CrLf)
        s.SomethingElse()
        Me.TextBox1.AppendText(p.S & ControlChars.CrLf)

with this

Public Class Class1
    Private _MyVar As Class2

    Public Sub New(ByRef MyVar As Class2)
        _MyVar = MyVar
    End Sub

    Public Sub SomethingElse()
        _MyVar.S &= "SomethingElse"
    End Sub
End Class

Christiaan Baes
Belgium

My Blog
"In a system where you can define a factor as part of a third factor, you need another layer to check the main layer in case the second layer is not the base unit." - jrbarnett

 

[ThatRickGuy]

hrm. Well then, I must have something screwed up.

Unfortunately, the stack is like 18 layers deep here, so finding the issue is a bit... challenging.

-Rick

VB.Net Forum forum796 forum855 ASP.NET Forum
I believe in killer coding ninja monkeys.

 

[ThatRickGuy]

Ahhhhh, I think I've found it.

If you pass in a null reference it will fail. Which as soon as I re-typed it on purpose I was like "doh! This ain't gonna work!"

if you change the Somethingelse method like so:

Public Sub SomethingElse()
    if _MyVar is nothing then _MyVar = new Class2 
    _MyVar.S &= "SomethingElse"
End Sub

Then run this code:

  Dim p As Class2
 'p is nothing
  Dim s As New Class1(p)
 'p is nothing  
  s.SomethingElse()
 'p is still nothing, even though the var inside s IS something

-Rick

VB.Net Forum forum796 forum855 ASP.NET Forum
I believe in killer coding ninja monkeys.

 

[ThatRickGuy]

Yup, between that and overwriting the reference else wheres in the stack, I finally managed to correct the issues.

-Rick

VB.Net Forum forum796 forum855 ASP.NET Forum
I believe in killer coding ninja monkeys.

 

[ThatRickGuy]

Wow, I just now got the email updates for this thread... weird.

-Rick

VB.Net Forum forum796 forum855 ASP.NET Forum
I believe in killer coding ninja monkeys.