– All objects have a property retaincount.
– copy, new, alloc and retain increase retain count by 1.
– release decreases retain count.
-autorelease decreases retaincount when the current run loop gets finished.
– Can create your own autorelease pools and drain them to reclaim memory.
Zones: Without zones small and large objects will be created together causing fragmentation. With zones, system creates two different zones – separate ones for different sizes of objects.
– Objects returned by Cocoa are normally autoreleased.
-in dealloc : [aProperty release]
or [self.property = nil]
bugs : app crash: something has been released or auto released and is being accessed
memory leak : memory was allocated but hasn’t been reclaimed even though not required
With ARC : Memory gets deallocated when all strong variables pointing to it are deallocated.
Strong, weak and unsafe_retained:
Strong : Valid till runtime and automatically released. Default for all local variables.
Weak : Zeroes ( sets to null ) the weak reference . So if a weak property points to a strong property and the strong property is released – the weak property is set to null.
unsafe_retained: Doesn’t get set to nil but set to a dangling location in memory.
While declaring them inline, use double underscore ..
Why is weak needed: To avoid circular references.
Now both have circular references