Real time blur effect for Navigation Bar

Apple has introduced new classes UIVisualEffectView and more to add translucency and blur effect on views from iOS 8.0 release.

Here how you can use it to add a blur effect to navigation bar or any other UIView:

Swift 5

func addBlurEffect() {
    let bounds = self.navigationController?.navigationBar.bounds
    let visualEffectView = UIVisualEffectView(effect: UIBlurEffect(style: .light))
    visualEffectView.frame = bounds ?? CGRect.zero
    visualEffectView.autoresizingMask = [.flexibleWidth, .flexibleHeight]
    self.navigationController?.navigationBar.addSubview(visualEffectView)        

    // Here you can add visual effects to any UIView control.
    // Replace custom view with navigation bar in the above code to add effects to the custom view.
}

Objective C Code:

- (void) addBlurEffect {
    // Add blur view
    CGRect bounds = self.navigationController.navigationBar.bounds;
    UIVisualEffectView *visualEffectView = [[UIVisualEffectView alloc] initWithEffect:[UIBlurEffect effectWithStyle:UIBlurEffectStyleLight]];
    visualEffectView.frame = bounds;
    visualEffectView.autoresizingMask = UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight;
    [self.navigationController.navigationBar addSubview:visualEffectView];
    self.navigationController.navigationBar.backgroundColor = [UIColor clearColor];
    [self.navigationController.navigationBar sendSubviewToBack:visualEffectView];

    // Here you can add visual effects to any UIView control.
    // Replace custom view with navigation bar in the above code to add effects to the custom view.
}

UPDATE:

If you find that after adding blur effect on navigationBar, navigation buttons are not visible then add below line after adding blurView code.

Swift:

self.navigationController?.navigationBar.sendSubview(toBack: visualEffectView)

Objective C:

[self.navigationController.navigationBar sendSubviewToBack:visualEffectView];