Shared Procedures Query

[gemel]

I have been reading sime material in .NET that throws some doubt on my
understanding of shared procedures.

With regard to object programming I assumed that variables declared
within a class were private to the class, each object would have
access to it's ver own copy of that variable. With regard to the
methods defined for a class, I assumed that these are shared among all
objects of the class, the code acting on the instances own copy of the
variables.

Now shared variables are attached to the class and not an instance of
the class and it makes sense that the methods that act on these should
be declared as shared, but only if I want to call them without having
an instance of the class. Can non-shared methods also be used on
shared variables?

John L

[Imran Koradia]

"gemel" <jo***@glenavon1.demon.co.uk> wrote in message
news:4b********************************@4ax.com...

I have been reading sime material in .NET that throws some doubt on my
understanding of shared procedures.

With regard to object programming I assumed that variables declared
within a class were private to the class, each object would have
access to it's ver own copy of that variable. With regard to the
methods defined for a class, I assumed that these are shared among all
objects of the class, the code acting on the instances own copy of the
variables.

Now shared variables are attached to the class and not an instance of
the class and it makes sense that the methods that act on these should
be declared as shared, but only if I want to call them without having
an instance of the class. Can non-shared methods also be used on
shared variables?

No. It'll throw up a compile time error. The only variables allowed in
shared methods are shared variables, variables local to the method and
parameters passed into the method.

Imran.

[Bonj]

> I have been reading sime material in .NET that throws some doubt on my

understanding of shared procedures.

With regard to object programming I assumed that variables declared
within a class were private to the class, each object would have
access to it's ver own copy of that variable.
You don't mean 'private', I think what you mean is called 'instance' members
as opposed to 'static' (Shared in VB.NET) members.
Whether a variable is Private or Public determines whether it can be seen by
code outside the class.
Whether a member variable is Shared or Instance determines whether there is
one for all instances of the class (for the whole program) or whether there
is a fresh one for every instance of the class.
Member functions can also be Shared or Instance, a Shared function can be
called without the need to have an instance of the class, but it thus can't
access variables (or other member functions) that are instance members.
With regard to the
methods defined for a class, I assumed that these are shared among all
objects of the class, the code acting on the instances own copy of the
variables.

Now shared variables are attached to the class and not an instance of
the class and it makes sense that the methods that act on these should
be declared as shared, but only if I want to call them without having
an instance of the class. Can non-shared methods also be used on
shared variables?

John L

[Bonj]

> Can non-shared methods also be used on

shared variables?
Yes, they can.
But obviously not the other way round - a shared method can't change a
non-shared variable, because it wouldn't know which instance of the class
(that's if any were even in existence) to modify the data of.


John L

[gemel]

Thanks for your prompt reply. Yes I did mean instance variable. But my
assumptions about code are correct aren't they? That is, methods of a
class whether shared or instance, exist only once, whereas the
instance variable belongs to each instance.

John L
On Tue, 12 Oct 2004 05:23:01 -0700, "Bonj"
<Bo**@discussions.microsoft.com> wrote:

Can non-shared methods also be used on
shared variables?

Yes, they can.
But obviously not the other way round - a shared method can't change a
non-shared variable, because it wouldn't know which instance of the class
(that's if any were even in existence) to modify the data of.

John L

[Imran Koradia]

Oops..I answered the wrong question :) I think Bonj already answered this
for you.

Imran.

No. It'll throw up a compile time error. The only variables allowed in
shared methods are shared variables, variables local to the method and
parameters passed into the method.

Imran.

[Imran Koradia]

"gemel" <jo***@glenavon1.demon.co.uk> wrote in message
news:c3********************************@4ax.com...

Thanks for your prompt reply. Yes I did mean instance variable. But my
assumptions about code are correct aren't they? That is, methods of a
class whether shared or instance, exist only once, whereas the
instance variable belongs to each instance.

That is correct. Method code is never copied - whether they are shared or
instance methods. And yes - instance variables belong to each individual
instance of the class.
Imran.

[Herfried K. Wagner [MVP]]

"gemel" <jo***@glenavon1.demon.co.uk> schrieb:

With regard to object programming I assumed that
variables declared within a class were private to the class,
each object would have access to it's ver own copy of that
variable.

That's only partially true. A class (in other words, one of its instances)
can have access to private variables declared in the class even if they
belong to another instance of the class.

--
Herfried K. Wagner [MVP]
<URL:http://dotnet.mvps.org/>

[Dennis]

How would they know which instance of the class to use unless they are
qualified by something like a global variable set a specific class instance?

"Herfried K. Wagner [MVP]" wrote:

"gemel" <jo***@glenavon1.demon.co.uk> schrieb:

With regard to object programming I assumed that
variables declared within a class were private to the class,
each object would have access to it's ver own copy of that
variable.

That's only partially true. A class (in other words, one of its instances)
can have access to private variables declared in the class even if they
belong to another instance of the class.

--
Herfried K. Wagner [MVP]
<URL:http://dotnet.mvps.org/>