iOS 7: What is UIBarButtonItem's default font?

Question

What is the default font of the title of a UIBarButtonItem with a style of UIBarButtonItemStyleDone?

The following just returns nil:

[doneBarButtonItem titleTextAttributesForState:UIControlStateNormal]

Answer 1

[UIFont boldSystemFontOfSize:17]

Note: I confirmed this by doing:

UIFont *font = [UIFont boldSystemFontOfSize:17];
[doneBarButtonItem setTitleTextAttributes:@{NSFontAttributeName: font}
                                 forState:UIControlStateNormal];

And then, I took screenshots of the before & after and compared them. They were identical.

Answer 2

You can retrieve the default font for a UILabel (which includes UIBarButton's title label) by querying

UIFont.systemFont(ofSize: UIFont.labelFontSize)