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// Accessorizer's default generated singleton code for class Foo | |
static Foo *sharedInstance = nil; | |
+ (void) initialize | |
{ | |
if (sharedInstance == nil) | |
sharedInstance = [[self alloc] init]; | |
} | |
+ (id) sharedFoo | |
{ | |
//Already set by +initialize. | |
return sharedInstance; | |
} | |
+ (id) allocWithZone: (NSZone *) zone | |
{ | |
//Usually already set by +initialize. | |
@synchronized(self) | |
{ | |
if (sharedInstance) | |
{ | |
//The caller expects to receive a new object, so implicitly retain it | |
//to balance out the eventual release message. | |
return [sharedInstance retain]; | |
} else | |
{ | |
//When not already set, +initialize is our caller. | |
//It's creating the shared instance, let this go through. | |
return [super allocWithZone: zone]; | |
} | |
} | |
} | |
- (id) init | |
{ | |
//If sharedInstance is nil, +initialize is our caller, so initialize the instance. | |
//If it is not nil, simply return the instance without re-initializing it. | |
if (sharedInstance == nil) | |
{ | |
self = [super init]; | |
if (self) | |
{ | |
//Initialize the instance here. | |
} | |
} | |
return self; | |
} | |
- (id) copyWithZone: (NSZone *) zone | |
{ | |
return self; | |
} | |
- (id) retain | |
{ | |
return self; | |
} | |
- (unsigned) retainCount | |
{ | |
return UINT_MAX; // denotes an object that cannot be released | |
} | |
- (void) release | |
{ | |
// do nothing | |
} | |
- (id) autorelease | |
{ | |
return self; | |
} |
// Apple's documented version (from Cocoa Fundamentals Guide) | |
// http://developer.apple.com/library/ios/#documentation/Cocoa/Conceptual/CocoaFundamentals/CocoaObjects/CocoaObjects.html%23//apple_ref/doc/uid/TP40002974-CH4-SW32 | |
static MyGizmoClass *sharedGizmoManager = nil; | |
+ (MyGizmoClass*)sharedManager | |
{ | |
if (sharedGizmoManager == nil) { | |
sharedGizmoManager = [[super allocWithZone:NULL] init]; | |
} | |
return sharedGizmoManager; | |
} | |
+ (id)allocWithZone:(NSZone *)zone | |
{ | |
return [[self sharedManager] retain]; | |
} | |
- (id)copyWithZone:(NSZone *)zone | |
{ | |
return self; | |
} | |
- (id)retain | |
{ | |
return self; | |
} | |
- (NSUInteger)retainCount | |
{ | |
return NSUIntegerMax; //denotes an object that cannot be released | |
} | |
- (void)release | |
{ | |
//do nothing | |
} | |
- (id)autorelease | |
{ | |
return self; | |
} |
no more overrides? I got those overrides from Apple's documentation some time ago.
@quavera if you read the thread the consensus here seems to be:
- that the Apple docs aren't great
- it's not necessary to enforce singleton-ness
- less is better.
(I'm not 100% in agreement with #2, and will probably put an NSAssert into my - init that tests to see if the sharedInstance
is nil and assert if not. Something like NSAssert( sharedInstance == nil, @"initializing a second copy of your singleton class, probably not what you want");
either as an assert or a debug NSLog message.)
no more overrides.
they're dangerous and scramble the normal ref counting mechanism (which isn't even available to you in ARC anyway).
If the user wants to retain/release the singleton - let him. It won't cause any harm at all.
If the user decides to release it - well that's a stupid programmer who isn't following the Obj-C reference counting rules. Not much you can or should do to prevent that.
ARC makes all this noise go away.
thanks to all for this discussion - I have a few switches (options) in the Accessorizer Singleton code gen interface. I can re-implement/add some custom options there. People just need to email me what they want and I'll do my best to accommodate. Lastly, if there's ever a question with the code generated by Accessorizer, do NOT hesitate to contact me via email so we can discuss, modify, improve etc.
editing the non blocks version to move static var out as both schwa and I generally do.