How to disable UIBarButtonItem?

If your toolbar has an IBOutlet (and you've checked to make sure it's non-nil), try:

[ [ [ myToolBar items ] objectAtIndex: myBarButtonItemIndex ] setEnabled:(NO) ];

You can disable the left navigation button from inside an UIViewController like this, without using any IBOutlet:

self.navigationItem.leftBarButtonItem.enabled = NO;

To disable the right navigation button:

self.navigationItem.rightBarButtonItem.enabled = NO;

Swift3

self.navigationItem.rightBarButtonItem?.isEnabled = false

I used a different solution (Swift 4.2) for my rightBarButtonItems.

I had 3 buttons so used a for loop, then made an extension of UINavigationItem so I could use it throughout my app.

extension UINavigationItem {
func setRightBarButtonItems(isEnabled:Bool){
    for button in self.rightBarButtonItems ?? [UIBarButtonItem()] {
        button.isEnabled = isEnabled
    }
}

Then i can call it from my TableViewController

navigationItem.setRightBarButtonItems(isEnabled: false)