Re: Is Apple's singleton sample code correct?
Re: Is Apple's singleton sample code correct?
- Subject: Re: Is Apple's singleton sample code correct?
- From: David Gimeno Gost <email@hidden>
- Date: Sat, 3 Dec 2005 14:01:38 +0100
I forgot the call to super in -dealloc, sorry:
On 3 Dec 2005, at 01:47, David Gimeno Gost wrote:
Let's suppose that, for whatever reasons, we want to modify our
singleton such that it can safely be used like this:
[MySingleton releaseSharedInstance];
[...]
- (void) dealloc
{
sSharedInstance = nil;
}
Just for the record, here's the complete implementation of this
variation (assuming there are no other mistakes, that is :-)):
@implementation MySingleton
static MySingleton* sSharedInstance = nil;
static BOOL sCanBeReleased = NO;
+ (MySingleton*) sharedInstance
{
@synchronized( self ) {
if ( sSharedInstance == nil ) {
// Note: calls -singletonInit instead of -init
sSharedInstance = [[MySingleton alloc] singletonInit];
sCanBeReleased = YES;
}
}
return sSharedInstance;
}
+ (void) releaseSharedInstance
{
@synchronized( self ) {
if ( sCanBeReleased ) {
[sSharedInstance release];
sCanBeReleased = NO;
}
}
}
- (id) init
{
// If we got here, the instance was created by alloc/init
// instead of +sharedInstance. Discard it and return the
// one created by +sharedInstance instead.
// Send a retain message to account for the
// call to alloc/init made by the client.
[self release];
self = [MySingleton sharedInstance];
return [self retain];
}
- (id) singletonInit
{
self = [super init];
if ( self != nil ) {
// Your singleton initialization goes here.
// This method will never be called more than once
// for the same object.
}
return self;
}
- (void) dealloc
{
// Your singleton deallocation code goes here.
// ...
sSharedInstance = nil;
[super dealloc];
}
@end
Regards.
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