objective c - week reference to autoreleased object not getting deallocated in case of NSString -

why temp object not released , set nil though declared __week. in case of person object working expected. nsstring objects memory life cycle handled differently? how?

@interface person : nsobject       @property(nonatomic, strong) nsstring *name;       - (instancetype)initwithname:(nsstring *)name;      + (person *)personwithname:(nsstring *)name; @end  @implementation person      - (instancetype)initwithname:(nsstring *)name {         if (self = [super init]) {             self.name = name;         }         return self;     }      + (person *)personwithname:(nsstring *)name {         return [[self alloc] initwithname: name];     } @end  - (void)viewdidload {       __weak nsstring *temp;       @autoreleasepool {           nsmutablearray *data = [[nsmutablearray alloc] initwithobjects:@"firststring", @"secondstring", nil];           temp = data[0];           [data removeobjectatindex:0];       }       nslog(@"%@", temp);//prints firststring instead of null        __weak person  *person ;       @autoreleasepool {           nsmutablearray *persons = [[nsmutablearray alloc] initwithobjects:[person personwithname:@"steve"], [person  personwithname:@"harry"], nil];           person = persons[0];           [persons removeobjectatindex:0];       }       nslog(@"%@", person.name);//prints null expected because person object deallocated, } 

constant strings never released. there other objects never released, nsnumber objects (on 64 bit versions, nsnumber objects).

it makes me wonder to. want if nsstring* becomes nil (which won't)?