Question

If I write directly something like this in implementation file:

UINavigationBar *navBar = [[UINavigationBar alloc] init];

In this case I haven’t set any property to my navBar, what will be its property/properties/nothing.

EDIT

-(IBAction) loginButtonPressed:(UIButton *)sender
{
UITabBarController *tabBar = [[UITabBarController alloc] init];
FirstScreen *f = [[FirstScreen alloc] initWithNibName:@"FirstScreen" bundle:nil];
UINavigationController *nav1 = [[UINavigationController alloc] initWithRootViewController:f];
nav1.title = @"FirstScreen";

SecondScreen *s = [[SecondScreen alloc] initWithNibName:@"SecondScreen" bundle:nil];
UINavigationController *nav2 = [[UINavigationController alloc] initWithRootViewController:s];
nav2.title = @"SecondScreen";

ThirdScreen *t = [[ThirdScreen alloc] initWithNibName:@"ThirdScreen" bundle:nil];
UINavigationController *nav3 = [[UINavigationController alloc] initWithRootViewController:t];
nav3.title = @"ThirdScreen";

NSArray *navControllers = [NSArray arrayWithObjects:f, s, t, nil];

tabBar.viewControllers = navControllers;

}

Answer 1

The properties of an object default to nil, or 0. But it is possible that these values have been changed in the init method.

For more information, you can always consult the documentation:

• tintColor : The default value is nil.

• barStyle : The default value is UIBarStyleDefault.

---

Edit

To answer your edited question, tabBar, nav2, … are local variables and not properties.

If you want them to be properties, you have first to declare such properties then, you have to access using self.tabBar, …

In the .h file:

// ...
@property (strong, nonatomic) UITabBarController *tabBar;
// ...

And in the .m file:

// ... @synthesize tabBar;

-(IBAction) loginButtonPressed:(UIButton *)sender
{
    self.tabBar = [[UITabBarController alloc] init];
    // ...
}