Need an array of object pointers

[Jack Addington]

Quite new to C# but I am getting quite confused with Array's and ArrayLists.
This is probably the same old iteration of a basic question but I can't seem
to find a clear answer/example of this case.

Basically I want a container that points to a set objects that I can then
interate through to group together a set of methods in a transaction. The
number of objects is unknown at compile time. I can't seem to come up with
a dynamic array of object references... only copies. I don't want 2
versions of the object. I'm getting confused between ArrayList and the need
to dynamically re-allocate the array each time I need to add a new object.

-------------
ie) object A = new object();
object B = new object();
object C = new object();

object[] list;

then how do I increase the size of the array so I can do:

object[1] = &A;
object[2] = &B;
object[3] = &C;

then my goal is to do

foreach( object l in list )
l.Save( )
---------------

Am I missing something with ArrayList? It isn't clear to me that
ArrayList.Add( object ) doesn't create another copy...

thx

[Morten Wennevik]

Hi Jack,

In C# things are handled by references, which is similar to pointers.

ArrayList.Add(myObject) adds myObject to the list, but myObject is just a reference not the object itself.

When creating an object array (object[]) you have to specify the size of it before you can use it.

object A = new object();
object B = new object();
object C = new object();

A, B and C are references to three object objects (the object class can get confusing to explain)

object[] list = new object[3];
list[0] = A; // arrays always start at position 0 in C#
list[1] = B;
list[2] = C;

list will now contain three references

If you don't know the size of the array it would be better to use an ArrayList

ArrayList list = new ArrayList();
list.Add(A);
list.Add(B);
list.Add(C);

list will now also contain three references

foreach(object o in list)
{
o.Save // except object doesn't have a method called save.
}

Once an object is created you handle it by passing its reference around.

--
Happy coding!
Morten Wennevik [C# MVP]

[Jack Addington]

perfect thanks... I managed to convince myself that ArrayList wasn't what I
wanted when all along it was perfect. As for the .Save() I was just making
an example... MyObject would have been a better thing to type up that
Object.

thanks again

jack
"Morten Wennevik" <Mo************@hotmail.com> wrote in message
news:opsdrrnp1mklbvpo@stone...

Hi Jack,

In C# things are handled by references, which is similar to pointers.

ArrayList.Add(myObject) adds myObject to the list, but myObject is just a reference not the object itself.
When creating an object array (object[]) you have to specify the size of it before you can use it.
object A = new object();
object B = new object();
object C = new object();

A, B and C are references to three object objects (the object class can get confusing to explain)
object[] list = new object[3];
list[0] = A; // arrays always start at position 0 in C#
list[1] = B;
list[2] = C;

list will now contain three references

If you don't know the size of the array it would be better to use an ArrayList
ArrayList list = new ArrayList();
list.Add(A);
list.Add(B);
list.Add(C);

list will now also contain three references

foreach(object o in list)
{
o.Save // except object doesn't have a method called save.
}

Once an object is created you handle it by passing its reference around.

--
Happy coding!
Morten Wennevik [C# MVP]

[Bob Grommes]

What is your target release date? Because Visual Studio 2005 (CLR 2.0) will
have generics, which gives you the List<T> class, which provides the dynamic
sizing benefits of the ArrayList without all the casting overhead;

using System.Collections.Generics;

List<MyClass> list = new List<MyClass>();

list.Add(new MyClass());
list.Add(new MyClass());

for (i = 0;i < list.Count;i++) {
list[i].DoSomething();
}

[ Unless things change in CLR 2.0, for is faster than foreach, but not
necessarily enough to worry about in practice most of the time; but I use it
here to more clearly illustrate that this is truly a list of MyClasses, and
doesn't have to be cast back from object. If you used a for loop with
ArrayList you'd have to do ((MyClass)list[i]).DoSomething(). ]

--Bob

"Jack Addington" <sh******@hotmail.com> wrote in message
news:ea*************@tk2msftngp13.phx.gbl...

Quite new to C# but I am getting quite confused with Array's and ArrayLists. This is probably the same old iteration of a basic question but I can't seem to find a clear answer/example of this case.

Basically I want a container that points to a set objects that I can then
interate through to group together a set of methods in a transaction. The
number of objects is unknown at compile time. I can't seem to come up with a dynamic array of object references... only copies. I don't want 2
versions of the object. I'm getting confused between ArrayList and the need to dynamically re-allocate the array each time I need to add a new object.

-------------
ie) object A = new object();
object B = new object();
object C = new object();

object[] list;

then how do I increase the size of the array so I can do:

object[1] = &A;
object[2] = &B;
object[3] = &C;

then my goal is to do

foreach( object l in list )
l.Save( )
---------------

Am I missing something with ArrayList? It isn't clear to me that
ArrayList.Add( object ) doesn't create another copy...

thx