Change font of back navigation bar button

Solution 1:

To change the appearance of the text in all UIBarButtonItems appearing in all UINavigationBars, do the following in application:didFinishLaunchingWithOptions:

[[UIBarButtonItem appearanceWhenContainedIn:[UINavigationBar class], nil] setTitleTextAttributes:
    @{UITextAttributeTextColor:[UIColor blackColor],
     UITextAttributeTextShadowOffset:[NSValue valueWithUIOffset:UIOffsetMake(0, 1)],
     UITextAttributeTextShadowColor:[UIColor whiteColor],
     UITextAttributeFont:[UIFont boldSystemFontOfSize:12.0]
    }
     forState:UIControlStateNormal];

UPDATE: iOS7 friendly version

NSShadow *shadow = [[NSShadow alloc] init];
shadow.shadowOffset = CGSizeMake(0.0, 1.0);
shadow.shadowColor = [UIColor whiteColor];

[[UIBarButtonItem appearanceWhenContainedIn:[UINavigationBar class], nil]
 setTitleTextAttributes:
 @{NSForegroundColorAttributeName:[UIColor blackColor],
   NSShadowAttributeName:shadow,
   NSFontAttributeName:[UIFont boldSystemFontOfSize:12.0]
   }
 forState:UIControlStateNormal];

Swift:

NOTE: this changes ALL instances of UIBarButtonItem, not just those contained within a UINavigationBar

UIBarButtonItem.appearance()
               .setTitleTextAttributes([NSFontAttributeName : ExamplesDefaults.fontWithSize(22)], 
                                       forState: UIControlState.Normal)

Swift3:

UIBarButtonItem.appearance()
     .setTitleTextAttributes([NSFontAttributeName: UIFont(name: "FontName-Regular", size: 14.0)!], 
                             for: .normal) 

Solution 2:

For anyone that did not fully got this to work, here is how i did it, including popped back to the Root ViewController in IOS7:

UIBarButtonItem *backBtn =[[UIBarButtonItem alloc]initWithTitle:@"Back" style:UIBarButtonItemStyleDone target:self action:@selector(popToRoot:)];
backBtn.title = @"Back";
[backBtn setTitleTextAttributes:[NSDictionary dictionaryWithObjectsAndKeys:
                                 [UIFont fontWithName:@"Chalkduster" size:15], NSFontAttributeName,
                                 [UIColor yellowColor], NSForegroundColorAttributeName,
                                 nil]
                       forState:UIControlStateNormal];

self.navigationItem.leftBarButtonItem=backBtn;

popToRoot ViewController:

- (IBAction)popToRoot:(UIBarButtonItem*)sender {
[self.navigationController popToRootViewControllerAnimated:YES];
}

Maybe someone may have use of this.

Solution 3:

Swift version of the all mentioned above (excerpt from the original answer) :

let customFont = UIFont(name: "customFontName", size: 17.0)!
UIBarButtonItem.appearance().setTitleTextAttributes([NSFontAttributeName: customFont], forState: .normal)

More goodies:
https://stackoverflow.com/a/28347428/469614