4 ms·

The big issue with singleton is that every time you have one db connection, one cache store, one file store, one of anything, you wind up needing a second one.

by herge 13y ago

The big issue with singleton is that every time you have one db connection, one cache store, one file store, one of anything, you wind up needing a second one. Make it easy to use the default one, but also make it easy to swap it out and use a different one.

pmelendez 13y ago
>" you wind up needing a second one" And by that moment it is not a singleton any more. The other way around is also true, you design your system to be scalable in db, cache store, etc. and you end using only one.
- masklinn 13y ago
  > And by that moment it is not a singleton any more. That's the point. If it's originally a singleton and you need a second instance, you're going to have a hard time. If it's a regular factory/object and you only ever use a single instance, chances are nothing will care (much, it may let some concurrency bugs or global state creep in)
  - pmelendez 13y ago
    >". If it's a regular factory/object and you only ever use a single instance, chances are nothing will care" That's true, although if it is a single instance but not global then you are not enjoying the benefits of the guaranteed of an unique instance. A well used singleton is a great tool that simplify things a lot.
    - masklinn 13y ago
      > A well used singleton Something which I've come to believe does not exist, the pattern itself is broken. Thus, > singleton is a great tool no. > that simplify things a lot. Paraphrasing Mencken, for every complex problem there is an answer that is clear, simple, and wrong. Singleton is ever that answer.
      - pmelendez 13y ago
        >Something which I've come to believe does not exist, the pattern itself is broken. >Paraphrasing Mencken, for every complex problem there is an answer that is clear, simple, and wrong. Singleton is ever that answer. Just because you haven't found a good use it doesn't mean it doesn't exist. And about Mencken... All he said is that you can't have Singletons without having a Global State (obvious) and apparently he has an strong allergy to global states. Global states are fine. Sure, they will make your tests harder but there are a lot of software that don't use unit test for legitimate reasons and hence don't have that problem.
- Nursie 13y ago
  One of these things is a problem you need to fix the other is a solution to a problem you don't have. It's not usually good to over-engineer or over-spec, but I'd rather have a little bit of that than a whole lot of software that can never scale.
  - pmelendez 13y ago
    >"One of these things is a problem you need to fix the other is a solution to a problem you don't have." That's true, but there are so many cases were a singleton is way more convenient than the alternatives, and not using it because it might "potentially" need to scale but never does sounds a bit silly to me. I am agreed though that you must be clear on the specifications, if a shadow of doubt appears is very to play it safe.

by herge 13y ago

pmelendez 13y ago

>" you wind up needing a second one" And by that moment it is not a singleton any more. The other way around is also true, you design your system to be scalable in db, cache store, etc. and you end using only one.

masklinn 13y ago
> And by that moment it is not a singleton any more. That's the point. If it's originally a singleton and you need a second instance, you're going to have a hard time. If it's a regular factory/object and you only ever use a single instance, chances are nothing will care (much, it may let some concurrency bugs or global state creep in)
- pmelendez 13y ago
  >". If it's a regular factory/object and you only ever use a single instance, chances are nothing will care" That's true, although if it is a single instance but not global then you are not enjoying the benefits of the guaranteed of an unique instance. A well used singleton is a great tool that simplify things a lot.
  - masklinn 13y ago
    > A well used singleton Something which I've come to believe does not exist, the pattern itself is broken. Thus, > singleton is a great tool no. > that simplify things a lot. Paraphrasing Mencken, for every complex problem there is an answer that is clear, simple, and wrong. Singleton is ever that answer.
    - pmelendez 13y ago
      >Something which I've come to believe does not exist, the pattern itself is broken. >Paraphrasing Mencken, for every complex problem there is an answer that is clear, simple, and wrong. Singleton is ever that answer. Just because you haven't found a good use it doesn't mean it doesn't exist. And about Mencken... All he said is that you can't have Singletons without having a Global State (obvious) and apparently he has an strong allergy to global states. Global states are fine. Sure, they will make your tests harder but there are a lot of software that don't use unit test for legitimate reasons and hence don't have that problem.
Nursie 13y ago
One of these things is a problem you need to fix the other is a solution to a problem you don't have. It's not usually good to over-engineer or over-spec, but I'd rather have a little bit of that than a whole lot of software that can never scale.
- pmelendez 13y ago
  >"One of these things is a problem you need to fix the other is a solution to a problem you don't have." That's true, but there are so many cases were a singleton is way more convenient than the alternatives, and not using it because it might "potentially" need to scale but never does sounds a bit silly to me. I am agreed though that you must be clear on the specifications, if a shadow of doubt appears is very to play it safe.