[Mono-list] Extending the singleton pattern in C#

[PRUTEANU Teodor Alexandru]

Hello Gaurav,

1.. Reasons for using this implementation for the singleton pattern: 
there's an article on msdn.microsoft.com, "Exploring the Sigleton 
Design Pattern", written by Mark Townsend, Feb 2002. The solution takes 
advantage from the CLI desing: removes lazy-inits, double locks (and so 
on) and it is *thread-safe*.

2.. I meant !extensible in the way that the current solution only provides 
one default ctor, so one user cannot instantiate the Singleton instance 
with his/her defined data.
I'm looking for smth like: 
public static readonly Instance = new Singleton 
(user-defined data extracted from custom attributes).
Hope you understand now my "extensibility" problem :-)

3.. Your solution does not satisfy me. Yes, I'm looking for more (2).

Best.

Alexandru Pruteanu
Faculty of Computer Science
Iasi, Romania
http://students.infoiasi.ro/~orion


> sealed class Singleton
> {
> public static readonly Instance = new Singleton ();
> private Singleton () {...}
> }
> class Test {Singleton obj = Singleton.Instance;}
>
> However, this technique does not seem to be so extensible, since 
> there's

    What do you mean by "extensible"? It's not quite clear here.

> no way to overload the private constructor (well, yes, but useless).

    Why useless?
    It's simpler than using attributes:

class Singleton
{
    public static type1 prop1;
    public static type2 prop2;

    private static Singleton instance = null;

    private Singleton()
    {
        // do something with prop1 and prop2.
    }

    public static Singleton Instance
    {
        get
        {
            if(instance == null)
            {
                instance = new Singleton();
            }
            return instance;
        }
    }
}


    I think this should satisfy you. Or are you looking for something 
more?



Happy hacking,
Gaurav
http://mastergaurav.virtualave.net/iitk
----------------------------

> One solution could be provided using attributes, e.g.
>
> class FooAttribute : Attribute
> {
> // whatever info I need
> }
> and later on,
> class Test
> {
> [Foo (...)]
> Singleton obj;
>
> public Test ()
> {
> obj = Singleton.Instance;
> }
> }
>
> My question is: how can I access (or transfer) the Foo declared data 
> in my
Singleton
> instance constructor? If that's not possible, do you have any other
suggestions
> on extending my singleton? There might be other solutions, but I don't
catch'em.
>
> Best,
>
> Alexandru Pruteanu
> Faculty of Computer Science
> Iasi, Romania
> http://students.infoiasi.ro/~orion
>
>
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