On the device, I've seen the GC be quite slow to collect. On the simulator /
desktop it collects instantly. You need to be aware that anything you release
a reference to can hang around longer than you intend.
Cheers,
Greg
On 28/08/2012, at 8:26 PM, Nic Wise <n...@fastchicken.co.nz> wrote:
> My understanding, and I may be wrong (quite likely, actually):
>
> Dispose is called when the object goes out of a using scope. That bit is
> deterministic - if you do this:
>
> using (var fff = new Foo())
> {
> }
>
> Dispose is always called at the end of that block. Same if you set it to
> null; HOWEVER the GC isn't deterministic, you don't know when it'll happen.
> In MT, I think it's quite aggressive, so it may be quite quickly, but it also
> may not be.
>
> However, if you have:
> var list = new List<Foo>();
> using (var foo = new Foo())
> {
> list.Add( foo );
> }
>
> At this point, the list has a reference to foo , but it's dispose has been
> called. If it had resources, they have been free'ed, but it's NOT going to be
> GC'ed, as the list has a reference.
>
> And to my (non) surprise, the C# docs have a good para on it :)
>
> http://msdn.microsoft.com/en-us/library/yh598w02.aspx
>
> You can instantiate the resource object and then pass the variable to the
> using statement, but this is not a best practice. In this case, the object
> remains in scope after control leaves the using block even though it will
> probably no longer have access to its unmanaged resources. In other words, it
> will no longer be fully initialized. If you try to use the object outside the
> using block, you risk causing an exception to be thrown. For this reason, it
> is generally better to instantiate the object in the using statement and
> limit its scope to theusing block.
>
> For one thing, I'd suggest you clear the event once you have called it -
> save's having a reference to another class (which may not be GC'able) keeping
> this one around. Or work out how to do a WeakReference event. Use an Action
> maybe?
>
> IDisposable has little to do with the GC - it's all about making sure
> resources are cleaned up properly. Normally, it calls dispose then goes out
> of scope, so the GC gets it, but if you keep a reference around, it'll not
> get GC'ed, even tho it HAS been disposed of.
>
> Does that make sense?
>
> N
>
>
>
>
> On Mon, Aug 27, 2012 at 9:56 PM, Phil Cockfield <p...@cockfield.net> wrote:
> I have a scenario where in one region of the app I have a collection managing
> models. In other places (ie, within Controllers) I have manipulation and
> lifecycle management of those models. A controller may dispose of a model.
>
> It would be clean for the collection to be alerted via an event when a model
> is disposed of, so I can do things like remove this disposed object from the
> collection.
>
>
>
>
> class Foo : NSObject
>
>
> {
>
> public event EventHandler Disposed;
>
>
>
>
> protected override void Dispose(bool disposing)
>
>
> {
>
> base.Dispose(disposing);
>
>
> if (disposing && Disposed != null) {
>
>
> // Alert listeners who might want to clean up state
>
>
> // based on the disposal of this instance.
>
>
> Disposed(this, new EventArgs());
>
>
> }
>
> }
> }
>
>
>
> Question: I'm wondering, is this a recipe for a memory leak?
>
> If I have something listening to a Disposed event, and then at the moment
> that object is disposed of, some other reference kicks off into action using
> the object. Would that pull it out of the queue for the GC to deal with?
>
> Or once Dispose has been called, is the end inexorable?
>
> I'm not doing any actual work with it - I'm just getting it out of my
> collection and clean up associated state.
>
> Thanks for any insights guys!
>
> --
> Phil Cockfield
>
>
>
>
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>
>
>
> --
> Nic Wise
> t. +44 7788 592 806 | @fastchicken | http://www.linkedin.com/in/nicwise
> b. http://www.fastchicken.co.nz/
>
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