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darkseed/gist:967518

Created May 11, 2011 22:21
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Singletons in Objective C
Raw
gistfile1.m
// A normal singleton
static AppInfo * sharedAppInfo = nil;
+ (AppInfo *) sharedAppInfo
{
if ( sharedAppInfo == nil )
{
[[self alloc] init];
}
return sharedAppInfo;
}
Raw
gistfile2.m
// A more thread safe singleton
static AppInfo * sharedAppInfo = nil;
+(AppInfo *) sharedAppInfo
{
@synchronized(self)
{
if ( sharedAppInfo == nil )
{
[[self alloc] init];
}
}
return sharedAppInfo;
}
Raw
gistfile3.m
// A slightly slower one but just as thread safe
static dispatch_once_t pred;
static AppInfo * sharedAppInfo = nil;
+(AppInfo *) sharedAppInfo
{
// more efficient way .
dispatch_once (&pred , ^{
sharedAppInfo = [[self alloc] init];
});
return sharedAppInfo;
}
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