objective-c：方法textFieldShouldBeginEditing忽略类属性

Question

我有一个视图控制器，在导航项中有一个UITextField。此视图控制器也是uitextfield的委托，因此它实现了-(BOOL)textFieldShouldBeginEditing:(UITextField *)textField。
但是这个方法里面有一点问题。当我想为这个类使用任何全局属性时，它们都是零，我有这样的：

- (id) initWithCoder:(NSCoder *)aDecoder {
    self = [super initWithCoder:aDecoder];
    if(self){
        FirstViewController *lvc = [[FirstViewController alloc] initWithNibName:@"FirstView" bundle:nil];
        SecondViewController *mvc = [[SecondViewController alloc] initWithNibName:@"SecondView" bundle:nil];
        ThirdViewController *lsc = [[ThirdViewController alloc] initWithNibName:@"ThirdView" bundle:nil];
        FourthViewController *fvc = [[FourthViewController alloc] initWithNibName:@"FourthView" bundle:nil];
        FifthViewController *svc = [[FifthViewController alloc] initWithNibName:@"FifthView" bundle:nil];

        viewControllers = [[NSArray alloc] initWithObjects:lvc, mvc, lsc, fvc, svc, nil];
        lastIndex = 0;

        isLogged = NO;

        [lvc release]; [mvc release]; [lsc release]; [fvc release]; [svc release];
    }
    return self;
}

- (BOOL)textFieldShouldBeginEditing:(UITextField *)textField{
    SearchView *searchView = [[SearchView alloc] initWithNibName:@"SearchView" bundle:nil andTextField:textField];
    // I need to set up delegate here
    // [searchView setDelegate:[viewControllers objectAtIndex:0]];
    // but viewControllers is nil in here
    AppDelegate *delegate = [[UIApplication sharedApplication] delegate];
    [delegate.navigationController pushViewController:searchView animated:YES];
    delegate = nil;
    [searchView release];
    return NO;
}

正如在代码中所解释的，viewControllers数组在textFieldShouldBeginEditing方法中是nil，所以我无法在我需要的地方设置委托...为什么属性在哪里？我能解决吗？
感谢。