> This is completely the wrong way to implement a property. The static
> variable will be shared between all instances. Here's how you should be
> doing a lazy loaded var:
>
> @implementation MyClass
> {
> NSDictionary *_someDictionary
> }
>
> - (NSDictionary *)someDictionary
> {
> static dispatch_once_t justOnce;
> dispatch_once(&justOnce, ^
> {
> someDictionary = [[NSDictionary alloc] initWithObjectsAndKeys: ……
> nil];
> });
> return someDictionary;
> }
I don't think this does what you think it does; my understanding is that
dispatch_once will execute only once for the lifetime of an app, so the code
you posted will only run once for the first object that requires is, and then
never run again, resulting in _dictionary being Nil in all other instances.
I understood the OP's request as wanting to implement a singleton, which, based
on your reading, may not be the case. dispatch_once will be fine for a
singleton, but if you need a thread-safe, lazily-instantiated read-only
property, maybe something like this will do the trick:
@implementation MyClass {
NSDictionary *_someDictionary
}
- (NSDictionary *) someDictionary {
@synchronized(self) {
if (!_someDictionary) {
_someDictionary = [[NSDictionary alloc] initWith… ]
}
}
return _someDictionary;
}
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