Sounds about right. In VB, we deal in "Value types" and "Reference types".
Value types are the basic types that hold their data within their own memory
allocation. Numeric types, booleans, chars, dates are all value types.
Reference types contain a pointer to another memory location that holds the
data. Arrays, strings, class types, etc. are all reference types. Here's
MSKB discussion on this:
http://msdn.microsoft.com/library/de...ueRefTypes.asp
"Workgroups" <noreply@domainless.com> wrote in message
news:Us6dndwlj5N2BkDfRVn-jw@speakeasy.net...[color=blue]
>I need some clarification with the whole "no pointers in VB.NET" thing,
>because it seems like there are "quazi-pointers" happening but I want to
>make sure I'm interpreting all this correctly.
>
> Here's a generic class declaration for the sake of example:
>
> Public clsClass
> 'properties, methods
> End Class
>
> And now some declarative snippits, followed by abstracts of what I think
> is happening:
>
> Dim objClass As clsClass
>
> That sets up something like this in memory:
>
> {objClass = Nothing} <- Can hold a memory address, but currently holds
> Nothing so far
>
> So as I understand it, this essentially creates something akin to a
> "pointer". It cannot be treated like a C++ pointer, but it is something
> of a pointer in the sense that it will "point" to memory.
>
> objClass = New clsClass
>
> Now it's set to an instance of an object, and so here's what I assume is
> now going on in memory:
>
> {@ address 1, clsClass instance} <- is now physically stored in the
> managed memory area
> {objClass = @1} <- now stores the memory address for lookup of the
> clsClass instance
>
> Dim objClass2 As clsClass = objClass
>
> Because they are references, this is what I assume is happening after this
> declaration:
>
> {@ address 1, clsClass instance} <- still physically stored in the managed
> memory area
> {objClass = @1} <- still storing the memory address for lookup
> {objClass2 = @1} <- now storing the same memory address for lookup as
> objClass
>
> Is this essentially correct? I still have only one actual instance, and
> two smaller pointers (well, references) available for lookups against the
> same instance. Let's add one more:
>
> Dim objClass3 as New clsClass
>
> {@ address 1, clsClass instance}
> {objClass = @1}
> {objClass2 = @1}
> {@ address 2, clsClass instance}
> {objClass3 = @2}
>
> So now two instances, three references (two of which point to the same
> instance). Now I start wandering out into stuff I'm not sure I
> understand, for example a HashTable. Here's my guess:
>
> Dim objHash as New HashTable:
>
> {@ memory address 1, clsClass instance}
> {objClass = 1}
> {objClass2 = 1}
> {@ memory address 2, clsClass instance}
> {objClass3 = 2}
> {@ memory address 3, HashTable instance}
> {objHash = 3}
>
> And then...
>
> objHash.Add("A", objClass2)
>
> {@ address 1, clsClass instance}
> {objClass = @1}
> {objClass2 = @1}
> {@ address 2, clsClass instance}
> {objClass3 = @2}
> {@ address 3, HashTable instance}
> {HashTable "A" = @1} <- ...something like that?
> {objHash = @3}
>
> Is the Hash table storing data in this fashion? Do I still have just one
> instance of clsClass?
>
> And finally does the garbage collector kill the instance for me once all
> the references are gone?
>
> objClass = Nothing
> objClass2 = Nothing
>
> {@ memory address 1, clsClass instance}
> {@ memory address 2, clsClass instance}
> {objClass3 = 2}
> {@ memory address 3, HashTable instance}
> {HashTable "A" = 1}
> {objHash = 3}
>
> Is the HashTable item "A" maintaining my instance @1?
>
> objHash.Remove(objHash("A"))
>
> [...GC runs]
>
> {@ address 2, clsClass instance}
> {objClass3 = @2}
> {@ address 3, HashTable instance}
> {objHash = @3}
>
> I'm starting a project using lots and lots of classes in multiple 2D
> arrays of hashtables and I want to make sure I have this stuff more or
> less correct in my mind before I start allocating memory like gangbusters.
>[/color]
