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Global variables of any flavor have that problem, that's why I would only do something like that for things that remain mostly constant throughout the program's lifetime.
Remember the Win32 hInstance parameter? It was passed to WinMain() as a parameter and remained unchanged from then on and you needed it for many Win32 API calls. The four bytes for a global variable were not much of a problem (yes, it was memory that was not cleaned up until the program ended) and it sure beats passing around that value to every window and dialog.
When memory hogging is under control, state is not problematic (or even constant), and when I need it all over the place, I will not go through the trouble of routing that object or variable to the remotest parts of the application.
I have lived with several Zen masters - all of them were cats.
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Marc Clifton wrote: nothing put into the dictionary ever gets garbage collected. Is there no way to handle that >?
«While I complain of being able to see only a shadow of the past, I may be insensitive to reality as it is now, since I'm not at a stage of development where I'm capable of seeing it.» Claude Levi-Strauss (Tristes Tropiques, 1955)
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OriginalGriff wrote: So I have a private constructor, a static Dictionary containing all created instances, and a static method which fetches the instance:
I only see a downside
you create an "instance" and fill it with data // no problems
...
later fetch your "instanse" and do the work // ...wow, that went pretty quick
all you've done is taken away the ability of the code editor/compiler to check the item exists and built in another opportunity for a hard to find run-time problem. (if you missed it check the spelling, because the compiler wont do that for you.)
and the upside isn't there, a separately declared list left empty takes few resoures.
Installing Signature...
Do not switch off your computer.
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OriginalGriff wrote: I hope not, I might have to stop using it ... Bullshit!
Design patterns were never intended to be the last word and the answer for everything. There is no law against coming up with your very own way of doing something, no matter what some gurus want to have you believe.
The SOLID faction would condemn you for breaching the single responsibility principle and using something akin to global variables and singletons. So what?
My personal sin is a message broker that I use in almost any UI. When compared to awkward wasteful automatic routing in a large UI tree or fragile code bloating manual routing, having a message broker as a singleton is a blessing. Some object registers with the broker to be notified when a specific message is sent, another object sends the message at some time and the broker looks up all subscribers and calls their event handlers. This is reasonably fast (no searching the entire UI tree) and absolutely unproblematic. The only weak spot is that an object better unregister its subscriptions when it is being destroyed, otherwise the broker may get bogged down servicing dead subscriptions.
Yes, global variables or singletons may be problematic, but sometimes you can have all of the benefits without any complications. I would immediately redesign if any complications materialized, but not simply for the purity of some design philosophy's sake. Why throw away something that has proven itself to be useful often enough?
But that's just me. I have always been conservative with redesigning and been building libraries, even when that meant to store machine code routines on cassette tapes and manually relocating them into a new program.
I have lived with several Zen masters - all of them were cats.
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A behavioral pattern?
Someone's therapist knows all about you!
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Interesting, Griff, I've played with some similar patterns. It probably was not your intent to show all of your code, but your mention of "heavy resources" made me wonder if you implement IDisposable, or the newer CLassName~ finalizer thingee.
«While I complain of being able to see only a shadow of the past, I may be insensitive to reality as it is now, since I'm not at a stage of development where I'm capable of seeing it.» Claude Levi-Strauss (Tristes Tropiques, 1955)
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IDisposable - and needless to say there are ways to remove items from the all collection to prevent things gumming up the garbage collector.
Bad command or file name. Bad, bad command! Sit! Stay! Staaaay...
AntiTwitter: @DalekDave is now a follower!
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Seems like an Appalachian version of DI, just missing a banjo duel
But fortunately we have the nanny-state politicians who can step in to protect us poor stupid consumers, most of whom would not know a JVM from a frozen chicken. Bruce Pierson Because programming is an art, not a science. Marc Clifton I gave up when I couldn't spell "egg". Justine Allen
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Hmm. I don't see anything wrong with it, other than the name "all " for the container, which isn't terribly descriptive.
I've used similar "patterns", where constructors and destructors maintain global constructs as a side effect. The global constructs usually simplify finding one of the instances in some way, or in accessing the entire collection of 'live' instances. In some cases I also use them for orderly shutdowns, to insure that all instances get destroyed properly.
For what it's worth, I've never read the GoF Patterns book.
Software Zen: delete this;
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Shoulda used a concurrent dictionary...
"(I) am amazed to see myself here rather than there ... now rather than then".
― Blaise Pascal
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OriginalGriff wrote: And it works really well. But ... is that a pattern?
Yes. Multiton. Been around a long time.
Multiton pattern - Wikipedia[^]
The general idea is a Singleton per 'context' where the definition of the context is up the implementation.
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A cunning way of asking a programming question in the Lounge!
The all field should be readonly , since you never replace it.
You should probably specify an explicit StringComparer for the dictionary, to make it more obvious that the key is case-sensitive.
I'd be inclined to move the Add to the static method, and leave the constructor alone. I'd also replace the ContainsKey / indexer pair with a single TryGetValue call:
public static MyClass Get(string name, List<string> data)
{
if (!all.TryGetValue(name, out MyClass instance)
{
instance = new MyClass(name, data);
all.Add(name, instance);
}
return instance;
}
And as Gerry said, if there's any possibility of the method being called by multiple threads, use a ConcurrentDictionary[^] instead:
private static readonly ConcurrentDictionary<string, MyClass> all = new ConcurrentDictionary<string, MyClass>(StringComparer.Ordinal);
public static MyClass Get(string name, List<string> data)
{
return all.GetOrAdd(name, key => new MyClass(key, data));
}
Let's hope your class doesn't contain any unmanaged or disposable resources, since you'd have no way of knowing when to clean them up.
"These people looked deep within my soul and assigned me a number based on the order in which I joined."
- Homer
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What are the virtues of a virtual machine?
... such stuff as dreams are made on
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They are virtually limitless.
Arguing with a woman is like reading the Software License Agreement. In the end, you ignore everything and click "I agree".
Anonymous
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What has to do with programming, your question? Virtually nothing!
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What machine? Where is it?
Installing Signature...
Do not switch off your computer.
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They are the main resource for virtual reality of course.
Don't they learn anything in school anymore these days.
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It gives a hope to all developer for a virtual success and money
cheers,
Super
------------------------------------------
Too much of good is bad,mix some evil in it
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My pal Will wanted a new machine but couldn't afford one. I told him to "Assume a virtual machine, if you have it not."
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Everyone knows that a virtual machine is virtuous. Even Lancelot used a virtual machine.
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The primary virtue of a virtual machine is that it's easy to restore its virtue.
Software Zen: delete this;
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Just wondering, what people think of the specs of the Razer Gaming Laptops for use as development machines?
We're looking for some fold ups and these look pretty strong contenders. Memory and graphics are high up on our needs as our product is highly visual and at the same time data heavy.
veni bibi saltavi
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Nagy Vilmos wrote: Memory and graphics are high up A computer can never have too much memory, nice and well. But what do you need high end graphics for? Are you really all writing graphics engines and blasting out as many high resolution frames per second as you can?
Nagy Vilmos wrote: highly visual and at the same time data heavy. That sounds more like drawing graphs in some reports to impress some old men in suits. Any chipset should render something like that and not start sweating over it.
I have lived with several Zen masters - all of them were cats.
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The UI is painting a lot of graphics and having a good graphics card - maybe not gamer quality, but good - makes it much smoother. With gammer machines, having a good spec means that they're generally good for developmnt.
veni bibi saltavi
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