ios UISearchBar 自动获取焦点

@property (weak, nonatomic) IBOutlet UISearchBar *searchBar;

- (void)viewWillAppear:(BOOL)animated
{
    [super viewWillAppear:animated];
    [self performSelector:@selector(setCorrectFocus) withObject:NULL afterDelay:0.8];
}

-(void) setCorrectFocus {
    [self.searchBar becomeFirstResponder];
}