Re: NSSound
Re: NSSound
- Subject: Re: NSSound
- From: Sherm Pendley <email@hidden>
- Date: Thu, 7 Nov 2002 17:55:11 -0500
On Wednesday, November 6, 2002, at 09:32 PM, Steve Mills wrote:
This works:
NSSound* snd = [NSSound alloc];
[snd retain];
[snd initWithContentsOfFile: fileName byReference: NO];
[snd play];
This should be:
NSSound *snd = [[NSSound alloc] initWithContentsOfFile: fileName
byReference: NO];
[snd play];
But this doesn't:
NSMutableData* data = [[NSMutableData dataWithContentsOfFile:
fileName] retain];
NSSound* snd = [[NSSound alloc] retain];
[snd initWithData: data];
[snd play];
And this should be:
NSMutableData *data = [NSMutableData dataWithContentsOfFile: fileName];
NSSound *snd [[NSSound alloc] initWithData: data];
[snd play];
The first [snd play] returns YES but the second returns NO. If it's the
same data, why does only the first method work? I even tried naming the
sound in the second method.
Note that in neither of the above corrections is snd retained - an
object obtained with init is not autoreleased, and so doesn't need to be
retained. Neither is data; unless you need to keep it to initialize
other sounds at some future point, it doesn't need to be retained.
That's not the cause of the problem, though - excessive retains don't
cause bugs, they simply cause your program to leak memory.
The problem is that you're calling retain too early, before the snd
object is initialized with init. That may not return anything useful. In
the first example, you're simply sending snd a retain message, so no
harm is done - other than possibly excessive memory usage. In the second
example, though, you're storing the result of the retain call, which may
be nil, in snd. A message sent to nil will always return nil, or zero,
which in the context of a BOOL type is NO.
To learn more about memory management in Objective-C/Cocoa, check out:
<URL:
file:///Developer/Documentation/Cocoa/TasksAndConcepts/ProgrammingTopics/MemoryMgmt/
index.html>
sherm--
If you listen to a UNIX shell, can you hear the C?
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| References: | |
| | >NSSound (From: Steve Mills <email@hidden>) |