iOS UIViewController=?iso-8859-1?Q?=2Cwhy_=22self=22_become_to_=22wild_pointer=22_in_viewDidU?==?iso-8859-1?Q?viewDidUnload=81H?=

iOS UIViewController,why "self" become to "wild pointer" in viewDidUnloadH

my code snippet:
- (void)viewDidUnload{
[super viewDidUnload];
self.statusView = nil;
self.tableView = nil;
self.noDataView = nil;
}
In a rare situation. My app crashed in line "self.noDataView = nil;". When
i debug by "po self",it seemed that it's pointing something other than
current controller. What is possible reason?
PS:self.tableView's delegate and dataSource is set to "self" in "init"
method.Is any relation with this?