1/2/06, Sanri Parov <sanri.parov (AT) tiscali (DOT) itwrote:
Hi everybody,

very fond of the large thread I've started with pointers, I beg your
pardon if I ask you another very silly question.
I've got to detach a new thread with

The problem stands in the fact that "" accepts only "id",
while I need to send a pointer ( PortAudioStream *stream) instead.
If I put "stream" in detachNewThreadSelector: the debugger complains
and halts, while if I set nil everything is ok.
How can I bypass this awful situation?

The NSValue class is capable of wrapping a pointer inside an object.

You can sometimes get away with simply casting a pointer or integer to
id, though it may not be a good idea, but
needs real objects
because it retains them when the thread is detached and releases them
when it terminates, and only real objects respond to retain and
release messages.

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2 jan 2006, at 11.48, Sanri Parov wrote:

PortAudio has nothing to do with NS as it's a plain C bunch
of functions that doesn't inherit from anything.

Where did you get the pointer to that stream? If it's owned by some
object, pass that object. If it's a global variable, or something you
can look up from a global function, don't pass anything at all.

2 jan 2006, at 12.08, Sanri Parov wrote:

[NSThread detachNewThreadSelector: @selector(playForSure:)
toTarget: nil :value];

The called selector is:

- (void)playForSure:(PortAudioStream *)stream;

but the selector is not called in any way.

Since you're sending the message to *nil*, that's not surprising at
all

Also, the method should now have this signature:
- (void) playForSure:(NSValue *) streamPtr;

j o a r

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02/gen/06, at 12:08, Sanri Parov wrote:

mmmhhhh
I've tried doing this:

NSValue *value;
value = [NSValue valueWithPointer:@encode(PortAudioStream *)];
[value retain];
[NSThread detachNewThreadSelector: @selector(playForSure:)
toTarget: nil :value];

Don't use @encode with valueWithPointer. It takes an actual pointer,
not a pointer type. Also, you shouldn't retain value,
detachNewThreadSelector will take care of it. Use something like this:

PortAudioStream *stream;

/* put code to initialize stream here */
[NSThread detachNewThreadSelector: @selector(playForSure:)
toTarget:self :[NSValue valueWithPointer:pas]];

assuming that the object which should handle the playForSure message
is self; otherwise, change it as needed.

The selector should be like this:
- (void)playForSure:(NSValue *)streamValue;
{
PortAudioStream *stream;
NSAutoreleasePool *pool;

pool = [[NSAutoreleasePool alloc] init];
stream = [streamValue pointerValue];

/* put your code here */

[pool release];
}

Camillo

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Jan 2, 2006, at 3:08 AM, Sanri Parov wrote:
mmmhhhh
I've tried doing this:

NSValue *value;
value = [NSValue valueWithPointer:@encode(PortAudioStream *)];
[value retain];
[NSThread detachNewThreadSelector: @selector(playForSure:)
toTarget: nil :value];

(1) Don't use @encode(). valueWithPointer: just takes a raw
pointer; it needs no information about what it is a pointing to.

(2) You are passing nil as the target for invocation of -playForSure:
in the detached thread. This effectively does absolutely nothing as
there is no way for NSThread to know whose -playForSure: method
should be invoked.

If -playForSure: is implemented on self, then pass self as the target.

b.bum

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