Typealias + extension examples for multiplatform development in Swift.

iOS.swift

import SwiftUI

/*
Put these in a file that is compiled for iOS only.

Note that these are just a few examples of things that worked well in my project.
They may or may not be useful to you, but they give an idea of how typealias + extensions
could be used to keep your code tidy.
*/

typealias UserInterfaceStyle = UIUserInterfaceStyle

extension Color {
    
    /// The color for the main background of your interface.
    static let systemBackground = Color(.systemBackground)
    
    /// The color for content layered on top of the main background.
    static let secondarySystemBackground = Color(.secondarySystemBackground)
    
}

typealias Device = UIDevice

extension UIDevice {
    
    /// Provides the operating system name, for example, iOS, iPadOS, or macOS.
    var multiplatformSystemName: String {
        switch userInterfaceIdiom {
        case .pad:
            // On iPad, the `systemName` property returns "iOS".
            return systemName.replacingOccurrences(of: "iOS", with: "iPadOS")
        default:
            return systemName
        }
    }
    
}

macOS.swift

import SwiftUI

/*
Put these in a file that is compiled for macOS only.

Note that these are just a few examples of things that worked well in my project.
They may or may not be useful to you, but they give an idea of how typealias + extensions
could be used to keep your code tidy.
*/

typealias UIApplication = NSApplication

extension NSApplication {
    
    /// Always returns `true` on macOS.
    var supportsAlternateIcons: Bool { true }
    
    /// Changes the icon the system displays for the app.
    ///
    ///  The error passed to the completion handler is always `nil` on macOS.
    func setAlternateIconName(_ alternateIconName: String?, completionHandler: ((Error?) -> Void)? = nil) {
        if let alternateIconName {
            NSApplication.shared.applicationIconImage = NSImage(named: alternateIconName)
            UserDefaults.alternateIconName = alternateIconName
        } else {
            NSApplication.shared.applicationIconImage = nil
            UserDefaults.resetAlternateIconName()
        }
        
        completionHandler?(nil)
    }
    
}

typealias UIAccessibility = NSAccessibility

extension NSAccessibility {
    
    /// Always returns `false` on macOS.
    static var isReduceMotionEnabled: Bool { false }
    
}

typealias UIColor = NSColor

extension Color {
    
    /// The color for the main background of the interface.
    static let systemBackground = Color("SystemBackgroundMacOS")
    
    /// The color for content layered on top of the main background.
    static let secondarySystemBackground = Color("SecondarySystemBackgroundMacOS")
    
}

enum UserInterfaceStyle: String, CaseIterable {
    
    /// The light interface style.
    case light
    
    /// The dark interface style.
    case dark
    
    /// An unspecified interface style.
    ///
    /// Choose this option when you want to follow the system's interface style.
    case unspecified
    
}

extension UserInterfaceStyle: LocalizedTitleConvertible {
    
    // Documentation inherited from protocol.
    var localizedTitle: String {
        switch self {
        case .light:
            return String(localized: "USER_INTERFACE_STYLE_CASE_LIGHT", comment: "Light")
        case .dark:
            return String(localized: "USER_INTERFACE_STYLE_CASE_DARK", comment: "Dark")
        case .unspecified:
            return String(localized: "USER_INTERFACE_STYLE_CASE_UNSPECIFIED_SHORT", comment: "System")
        }
    }
    
}

extension UserInterfaceStyle: Identifiable {
    
    // Documentation inherited from protocol.
    var id: Self { self }
    
}

struct Device {
    
    /// Represents the current device.
    static let current = Device()
    
    /// The model of the device.
    ///
    /// Returns "Mac" on macOS.
    var model: String { "Mac" }
    
    /// The name of the device.
    ///
    /// Provides the full user name on macOS, for example, "Bob McBobface".
    var name: String {
        ProcessInfo.processInfo.fullUserName
    }
    
    /// Provides the operating system name, for example, iOS, iPadOS, or macOS.
    ///
    /// Returns "macOS" on macOS.
    var multiplatformSystemName: String { "macOS" }
    
    /// Provides system OS version, for example, 13.2.
    var systemVersion: String {
        let majorMinorVersionString = "\(ProcessInfo.processInfo.operatingSystemVersion.majorVersion).\(ProcessInfo.processInfo.operatingSystemVersion.minorVersion)"
        let patchVersion = ProcessInfo.processInfo.operatingSystemVersion.patchVersion
        
        if patchVersion > 0 {
            return majorMinorVersionString + ".\(patchVersion)"
        } else {
            return majorMinorVersionString
        }
    }
    
}