I've tried multiple ways. I know the dictionary is NULL, as the console also prints out when I break there. Yet when I put it in an if( ) it doesn't trigger.
([myDict count] == 0) //results in crash
(myDict == NULL)
[myDict isEqual:[NSNull null]]
It looks like you have a dangling or wild pointer.
You can consider Objective-C objects as pointers to structs.
You can then of course compare them with
NULL, or with other pointers.
( myDict == NULL )
( myDict == [ NSNull null ] )
are both valid.
The first one will check if the pointer is
NULL is usually defined as a
void * with a value of 0.
Note that, for Objective-C objects, we usually use
nil is also defined as a
void * with a value of 0, so it equals
NULL. It's just here to denote a
NULL pointer to an object, rather than a standard pointer.
The second one compares the address of
myDict with the singleton instance of the
NSNull class. So you are here comparing two pointers values.
So to quickly resume:
NULL == nil == Nil == 0
[ NSNull null ] is a valid instance:
NULL != [ NSNull null ]
Now about this:
( [ myDict count ] == 0 )
It may crash if you have a wild pointer:
NSDictionary * myDict; [ myDict count ];
Unless using ARC, it will surely crash, because the
myDict variable has not been initialised, and may actually point to anything.
It may also crash if you have a dangling pointer:
NSDictionary * myDict; myDict = [ [ NSDictionary alloc ] init ]; [ myDict release ]; [ myDict count ];
Then you'll try to send a message to a deallocated object.
Sending a message to
NULL is always valid in Objective-C.
So it depends if you want to check if a dictionary is
nil, or if it doesn't have values (as a valid dictionary instance may be empty).
In the first case, compare with
nil. Otherwise, checks if count is 0, and ensure you're instance is still valid. Maybe you just forgot a retain somewhere.