TrackDetailsViewController.swift

import UIKit

class TrackDetailsViewController: UIViewController {
    
    @IBOutlet weak var trackNameHeaderLabel: UILabel!
    
    @IBOutlet weak var artistNameHeaderLabel: UILabel!
    
    // ...
    
    var track: Track?
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        title = NSLocalizedString("trackDetailsTitle", comment: "")
        
        if let track = track {
            trackNameHeaderLabel.text = 
                getLocalizedHeaderText(key: "trackNameHeader")
            
            artistNameHeaderLabel.text =
                getLocalizedHeaderText(key: "artistNameHeader")
            
            releaseDateHeaderLabel.text =
                getLocalizedHeaderText(key: "releaseDateHeader")
            
            // ...
        }
    }
     
    // ...
    
    fileprivate func getLocalizedHeaderText(key: String) -> String {
        return NSLocalizedString(key, comment: "")
            .localizedUppercase
    }
}