by Miško Hevery Singletons are Pathological Liars and Where Have All the Singletons Gone I feel obliged to to do some root cause analysis.Singletons are Pathological Liars ) The root problem is not the Singleton design pattern, the root problem here is the global reference to singleton. But the moment you get rid of the global variable you get rid of the Singleton design pattern. So from my point of view blaming Singletons or blaming global state is one and the same. You can't have a Singleton design pattern and at the same time not have the global state.
As you said, I think "most developers recognize" that old-school global variables (like those heavily abused in C) are a blight. But this is really a bit of a nostalgic argument, and I don't know that it's directly relevant to Singletons.
ReplyDeleteSingletons can certainly be abused, but I'd say they're one step up from C-style global vars. At least they let us categorize global vars and behaviors into classes, to give hints as to purpose and improve serviceability.
I think the core problem really stems from (what is incidentally your primary viewpoint) testability concerns. And from there I can agree with you, and have been reviewing your previous articles for suggestions on how to improve this issue.
Nonetheless, I think it's a mistake to wholly throw out Singletons as remnants of caveman code. They have their place, and they are an improvement over what "most developers" think of as global state.
Let's for the sake of argument say that Singleton is considered harmful. Just as Quirky asked, what can be done? Some concrete tips would be really handy I think.
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