The design patterns in GoF hardly hang on the Singleton. (Keep in mind that ’singleton’ is a single instance of a class (no problem), and ‘Singleton’ is the design pattern.) Assuming that you’re referring to the Singleton design pattern, the problem centers around the global nature of the design as noted.

Rather than using the Singleton, my key focus is on the Client. Some of the design patterns include the Client as part of the design and others include it as implied (such as the Visitor which I’m currently working on.) Still others give no clue in the class diagram where the Client sends initial requests. However, for me the key connection is the relationship between the Client and the design pattern and a Singleton simply causes problem. I’ve added a diagram at the bottom on the original post to show my thinking on the issue.

Thank you for bringing up this issue. It was one of the many that led to my own head scratching concerning the Singleton.

Kindest regards,
Bill

I’m glad to hear the post was helpful. Right now I’m working on the Visitor pattern, and it is a nice return to a pattern that is very helpful and intriguing at the same time.

Take care,
Bill

Excellent article.

I decided not to use Singletons a while back due to the inelegance and all the attached problems these AS3 “workarounds” create. But I had still not entirely made up my mind about them and probably would have gone back to trying to use them again.

Frankly, it’s a load off my mind to get some very solid reasons as to why not to use them — with the static variables simile being the solid rock at the core of your argument, IMO.

Thanks for sharing.

I suppose it’s easier to think of using global variables instead of a Singleton. Had I suggested we never use global variables, I doubt that anyone would have cared. It would be one of those tell us something we don’t know reactions. Because the Singleton is a global variable wrapped in a design pattern, we tend to get riled up.

I’m glad the post makes sense to you. Thanks for participating in the discussion.

Kindest regards,
Bill

Don’t feel bad about still learning best practices in OOP. As soon as I stop learning, it’s not going to be fun any more. (And I plan on a lot more fun!)

Many developers have the same question that you have: If not a Singleton, then what? Miško Hevery has a good article on that question and provides answers. Take a look at:

http://misko.hevery.com/2008/08/21/where-have-all-the-singletons-gone/

It doesn’t specifically address a manager class, but it does address similar issues.

Take care,
Bill