Custom font for MKAnnotationView Callout

Question

Fortunately, the standard callout view for an MKAnnotationView meets our needs - title, subtitle, leftCalloutAccessoryView

Answer 1

Since I needed the Swift version - here it is. Also, you have to call setNeedsLayout() on didAddSubview() because otherwise when you deselect and reselect the annotation layoutSubviews() is not called and the callout has its old font.

// elsewhere, in a category on UIView.
// thanks to this answer: http://stackoverflow.com/a/25877372/607876

typealias ViewBlock = (_ view: UIView) -> Bool

extension UIView {
  func loopViewHierarchy(block: ViewBlock?) {

    if block?(self) ?? true {
      for subview in subviews {
        subview.loopViewHierarchy(block: block)
      }
    }
  }
}

// then, in your MKAnnotationView subclass

class CustomFontAnnotationView: MKAnnotationView {

  override func didAddSubview(_ subview: UIView) {
    if isSelected {
      setNeedsLayout()
    }
  }

  override func layoutSubviews() {

    // MKAnnotationViews only have subviews if they've been selected.
    // short-circuit if there's nothing to loop over

    if !isSelected {
      return
    }

    loopViewHierarchy { (view: UIView) -> Bool in
      if let label = view as? UILabel {
        label.font = labelFont
        return false
      }
      return true
    }
  }
}