IOS Memory leak in class method - iphone

Question

In your opinion if I have a singleton subclass of NSObject being initialised with parameters like this:
- (MyObject *) initWithSomeParam:(NSString *)param{
self = [super init];
if (SharedInstance == nil){
SharedInstance = [super init];
SharedInstance.someProperty = param;
}
return self;
}
+ (MyObject *) objectWithSomeParam:(NSString *)param{
return [[self alloc] initWithSomeParam:param];
// Will the alloc cause a leak?
}
The user doesn't have access to the instance method, just the class. Thanks.

Answer 1

That's not the normal way of implementing a singleton and you are breaking the convention of init. Better would be to create a sharedInstance class method and leave the initWithParam method to be more conventional:
static MyObject *_sharedInstance = nil;
+ (MyObject *)sharedInstance:(NSString *)param
{
if (_sharedInstance == nil)
{
_sharedInstance = [MyObject alloc] initWithParam:param];
}
return _sharedInstance;
}
// This must be called during app termination to avoid memory leak
+ (void)cleanup
{
[_sharedInstance release];
_sharedInstance = nil;
}
- (id)initWithParam:(NSString *)param
{
self = [super init];
if (self != nil)
{
self.someProperty = param;
}
return self;
}
However, even that doesn't seem very comfortable; i.e. what happens if the user calls sharedInstance with a different parameter? Perhaps you want to keep a NSMutableDictionary of the initialized objects and create/return them depending on the parameter?
If so, you would do:
static NSMutableDictionary _sharedInstances = [[NSMutableDictionary alloc] init];
+ (MyObject *)sharedInstance:(NSString *)param
{
MyObject *obj = [_sharedInstances objectForKey:param];
if (obj == nil)
{
obj = [[MyObject alloc] initWithParam:param];
[_sharedInstances setObject:obj forKey:param];
}
return obj;
}
// This must be called during app termination to avoid memory leak
+ (void)cleanup
{
[_sharedInstances release];
_sharedInstances = nil;
}