1.iOS6之前的做法

NSValue *value = [NSValue valueWithNonretainedObject:myObj]; 
[array addObject:value];

2.現在的做法
=== Code ===

NSObject *object = [[NSObject alloc] init];
NSLog(@"object.retainCount %i", object.retainCount);
NSHashTable *hashTable = [NSHashTable weakObjectsHashTable];
[hashTable addObject:object];
NSLog(@"object.retainCount %i", object.retainCount);

==== Log ===
2014-04-01 15:05:41.715 test[9915:60b] object.retainCount 1
2014-04-01 15:05:41.715 test[9915:60b] object.retainCount 1