Decoupling

Decoupling.swift

struct Document {
    let identifier: Int
}
enum Mode: String {
    case edit = "edit"
    case view = "view"
}
protocol URLOpening {
    func open(_ url: URL, options: [UIApplication.OpenExternalURLOptionsKey : Any], completionHandler completion: ((Bool) -> Void)?)
}
extension UIApplication: URLOpening {
    // Nothing needed here!
}

class DocumentOpener {
    let urlOpener: URLOpening
    
    init(urlOpener: URLOpening = UIApplication.shared) {
        self.urlOpener = urlOpener
    }
    func openUrl(document: Document, mode: Mode) {
        let stringURL = "myappscheme://open?id=\(document.identifier)&mode=\(mode.rawValue)"
        guard let url = URL(string: stringURL) else {
            return
        }
        urlOpener.open(url, options: [:], completionHandler: nil)
    }
}