Попробуйте этот кусок кода для консольного приложения OS X:
//
// main.m
//
#import <Foundation/Foundation.h>
uint objectsAlive = 0;
uint totalObjects = 0;
@interface TestObject : NSObject
@end
@implementation TestObject
{
uint myIx;
}
- (id)init
{
// NSAssert([NSThread currentThread] == [NSThread mainThread], @"Not on the main thread");
self = [super init];
if (self)
{
objectsAlive++;
totalObjects++;
myIx = totalObjects;
NSLog(@"Object with id=%u created; alive objects %u", myIx, objectsAlive);
}
return self;
}
- (void)dealloc
{
objectsAlive--;
NSLog(@"Object with id=%u is being destroyed by ARC; alive objects will become %u", myIx,objectsAlive);
}
@end
int main(int argc, const char * argv[]) {
// default global autorelease pool
@autoreleasepool {
NSHashTable * testHashMap = [NSHashTable weakObjectsHashTable];
// weakObjectsHashTable - according to Apple docs, entries are not necessarily purged right away when the weak object is reclaimed, and we can observe this behavior here - some entries stay alive until last autorelease
// comment out the line above and uncomment the line below to observe different behavior with strong references in NSHashTable
// NSHashTable * testHashMap = [[NSHashTable alloc] init];
// nested autoreleasepool to ensure that the objects added to the testHashMap are released by ARC
@autoreleasepool {
for(int i = 0; i < 10;i++) {
TestObject * obj = [[TestObject alloc] init];
[testHashMap addObject: obj];
NSLog(@"Count in hash table inside additions scope is %lu",
(unsigned long)testHashMap.count);
}
NSLog(@"Count in hash table inside @autoreleasepool is %lu",
(unsigned long)testHashMap.count);
NSLog(@"Objects in hash table inside of @autoreleasepool are %@",
testHashMap.allObjects);
NSLog(@"Exiting inner autorelease pool...");
}
// objects in NSHashTable also were released, according to dealloc logs in TestObject, but count is still lagging behind (shows 2)
NSLog(@"Count in hash table outside of @autoreleasepool is %lu",
(unsigned long)testHashMap.count);
// this should indeed show that NSHashTable with weakObjectsHashTable is empty, despite count=2
NSLog(@"Objects in hash table outside of @autoreleasepool are %@",
testHashMap.allObjects);
NSLog(@"Exiting outer autorelease pool, ecpect all objects in strong ref NSHashTable to die...");
}
return 0;
}
Вы должны увидеть, что HashMap действительно пуст и объекты некорректной уничтожены прямо внутри цикла for
, где их сильные ссылки заброшены. Но проблема в том, что у .count
собственность - она лежит, говоря, что есть записи, хотя allObjects
ничего не возвращает.
'string' - частный случай, см. Здесь http://stackoverflow.com/questions/10922888/weak-nsstring-variable-is-not-nil-after-setting-the-only-strong-reference-to -nil и попробуйте версию с NSObject. – JustAMartin