subclassing singleton???

[faiza haris]

is that possible??
any good reference site???
thanx

[Frank Carver]

It's perfectly reasonable to subclass a Singleton. "Singleton" is just a pattern, not an actual class, so you are free to implement it how you wish. I am interested in whay you feel you need to subclass a Singleton, though. Can you give us any more information about what you are doing with this pattern?

[shailesh sonavadekar]

Faiza ,singleton pattern is used when you want to have one class only , not more , not less. As , Frank said you can subclass it. You can get more information about this in " Gang Of FOur " book , i.e. " Design Patterns " by eric gamma etc.
Like Frank , I am also curious about the utility of this in your project. Can you please elaborate about your purpose , if it is ok for you.

[faiza haris]

Well , I was reading an article on singleton, and had this question as to why and when emerges need of subclassing a singleton. Plz can u give a case scenario.
As regards any project.......well i might be given a project and was checking whether to go in patterns or EJB, Servlets cuz i have rational rose, uml experience.
Someone help decide!!!
any article for subclassing singleton? wht are the drawbacks for that?

[John Wetherbie]

I worked on a project where I remember discussing with someone about them subclassing a singleton class that they had. Can't really remember the context, so that probably isn't too helpful.
I think the most interesting thing about subclassing a singleton is whether you want the derived class to be a singleton or not since singleton-ness (is that a word?) is not inherited. In the case where the derived class is not a singleton then the question of why composition wouldn't work comes up.
Still can't remember why they wanted to do that subclassing. Guess I'll give up.