Problem sending notification from C callback function
-
Greetings.
I'm having a little problem due to lack of knowledge here.
I have this callback from DiskArbritation framework
and I would like to send a notification to my app.
but it does not seem to work.
the callback is registered like this.
daSession = DASessionCreate(kCFAllocatorSystemDefault);
DASessionScheduleWithRunLoop(daSession, [[NSRunLoop currentRunLoop]
getCFRunLoop], kCFRunLoopCommonModes);
DARegisterDiskDisappearedCallback(daSession, NULL,
&DiskDisappearedCallback, (void *)self);
the callback is defined like this.
void DiskDisappearedCallback(DADiskRef disk, void *context){
CFDictionaryRef diskDescription = DADiskCopyDescription(disk);
NSDictionary *nsDiskDescription = (NSDictionary *)diskDescription;
NSString *name = [nsDiskDescription valueForKey:@"DAVolumeName"];
NSString *type = [nsDiskDescription valueForKey:@"DAVolumeKind"];
NSString *path = [nsDiskDescription valueForKey:@"DAVolumePath"];
[[NSNotificationCenter defaultCenter]
postNotificationName:ADD_REMOVE_NOTIFICATION object:nil userInfo:nil];
}
Obviously, default center does not exist in the callback, but i cant
seem to typecast the context to
my object type and retrieve the notification center from the object. i
just do not know how to do it.
could someone enlighten me please ?
thank you Sandro Noel. -
Sandro Noel (<sandro.noel...>) on 2009-01-08 8:57 PM said:
> DARegisterDiskDisappearedCallback(daSession, NULL,
> &DiskDisappearedCallback, (void *)self);
Is your application garbage collected? If so, passing self as the
context could be problematic. See:
<http://developer.apple.com/documentation/Cocoa/Conceptual/
GarbageCollection/Articles/gcUsing.html#//apple_ref/doc/uid/TP40008006-SW4>
Sean -
On Jan 8, 2009, at 7:57 PM, Sandro Noel wrote:
> I have this callback from DiskArbritation framework
> and I would like to send a notification to my app.
> but it does not seem to work.
Does not seem to work in what way? Are you getting compiler errors or
warnings? Crashes at runtime? What?
> the callback is defined like this.
> void DiskDisappearedCallback(DADiskRef disk, void *context){
> CFDictionaryRef diskDescription = DADiskCopyDescription(disk);
> NSDictionary *nsDiskDescription = (NSDictionary *)diskDescription;
>
> NSString *name = [nsDiskDescription valueForKey:@"DAVolumeName"];
> NSString *type = [nsDiskDescription valueForKey:@"DAVolumeKind"];
> NSString *path = [nsDiskDescription valueForKey:@"DAVolumePath"];
>
> [[NSNotificationCenter defaultCenter]
> postNotificationName:ADD_REMOVE_NOTIFICATION object:nil userInfo:nil];
> }
>
> Obviously, default center does not exist in the callback,
Actually, I don't know what you mean here, so it's far from obvious.
The default notification center is a singleton. It always "exists" in
the sense that you can always retrieve it using [NSNotificationCenter
defaultCenter], just as you have.
> but i cant seem to typecast the context to
> my object type and retrieve the notification center from the object.
> i just do not know how to do it.
Well, since the default notification center is a singleton, it is
effectively globally available. You don't need to stash a reference
to it in your object and retrieve it from there.
With regard to the general question of how you can message the object
passed in context: given that the context is an object pointer, you
can just cast it:
id myObject = (id)context;
[myObject someMethod:someArgument];
If you have a more specific type than id, go ahead and use that.
Regards,
Ken -
Ken thank you.
the problem was elsewhere in a dictionary key name...
thank you for your help!!!
Sandro Noel.
On 9-Jan-09, at 2:09 AM, Ken Thomases wrote:
> On Jan 8, 2009, at 7:57 PM, Sandro Noel wrote:
>
>> I have this callback from DiskArbritation framework
>> and I would like to send a notification to my app.
>> but it does not seem to work.
>
> Does not seem to work in what way? Are you getting compiler errors
> or warnings? Crashes at runtime? What?
>
>
>> the callback is defined like this.
>> void DiskDisappearedCallback(DADiskRef disk, void *context){
>> CFDictionaryRef diskDescription = DADiskCopyDescription(disk);
>> NSDictionary *nsDiskDescription = (NSDictionary *)diskDescription;
>>
>> NSString *name = [nsDiskDescription valueForKey:@"DAVolumeName"];
>> NSString *type = [nsDiskDescription valueForKey:@"DAVolumeKind"];
>> NSString *path = [nsDiskDescription valueForKey:@"DAVolumePath"];
>>
>> [[NSNotificationCenter defaultCenter]
>> postNotificationName:ADD_REMOVE_NOTIFICATION object:nil
>> userInfo:nil];
>> }
>>
>> Obviously, default center does not exist in the callback,
>
> Actually, I don't know what you mean here, so it's far from obvious.
>
> The default notification center is a singleton. It always "exists"
> in the sense that you can always retrieve it using
> [NSNotificationCenter defaultCenter], just as you have.
>
>
>> but i cant seem to typecast the context to
>> my object type and retrieve the notification center from the
>> object. i just do not know how to do it.
>
> Well, since the default notification center is a singleton, it is
> effectively globally available. You don't need to stash a reference
> to it in your object and retrieve it from there.
>
> With regard to the general question of how you can message the
> object passed in context: given that the context is an object
> pointer, you can just cast it:
>
> id myObject = (id)context;
> [myObject someMethod:someArgument];
>
> If you have a more specific type than id, go ahead and use that.
>
> Regards,
> Ken
>
