Cross Platform Property Wrapper

README.md

Cross Platform Property Wrapper

Javier Soto posted a tweet which showed a clever use property wrappers for supporting cross platform development. It has a lot of potential but does not appear to work when the value is not a short reference. It is also not clear how well it would work with the compiler when targeting each platform.

---

Playground.swift

import Foundation

#if canImport(UIKit)
import UIKit
#elseif canImport(AppKit)
import AppKit
#elseif canImport(WatchKit)
import WatchKit
#endif

@propertyWrapper
public struct PlatformDependentValue<T> {
    public var wrappedValue: T { self.resolvedValue }
    private let resolvedValue: T
    #if os(iOS) || os(macOS) || os(watchOS) || os(tvOS)
    init(iOS: @autoclosure () -> T, macOS: @autoclosure () -> T,
         watchOS: @autoclosure () -> T, tvOS: @autoclosure () -> T) {
        #if os(iOS)
        resolvedValue = iOS()
        #elseif os(macOS)
        resolvedValue = macOS()
        #elseif os(watchOS)
        resolvedValue = watchOS()
        #elseif os(tvOS)
        resolvedValue = tvOS()
        #endif
    }
    #endif
}

enum CrossPlatform {
    static func deviceName() -> String {
        #if canImport(UIKit)
        UIDevice.current.name
        #elseif canImport(AppKit)
        ProcessInfo.processInfo.hostName
        #elseif canImport(WatchKit)
        WKInterfaceDevice.current.name
        #endif
    }

    static func devicModel() -> String {
    #if canImport(UIKit)
    UIDevice.current.model
    #elseif canImport(AppKit)
    "Mac"
    #elseif canImport(WatchKit)
    WKInterfaceDevice.current.model
    #endif
}

    static func systemVersion() -> String {
        #if canImport(UIKit)
        UIDevice.current.systemVersion
        #elseif canImport(AppKit)
        ProcessInfo.processInfo.operatingSystemVersionString
        #elseif canImport(WatchKit)
        WKInterfaceDevice.current.systemVersion
        #endif
    }

    static func systemName() -> String {
        #if canImport(UIKit)
        UIDevice.current.systemName
        #elseif canImport(AppKit)
        ProcessInfo.processInfo.hostName
        #elseif canImport(WatchKit)
        "Darwin"
        #endif
    }
}

struct Device {
    @PlatformDependentValue(iOS: CrossPlatform.deviceName(),
                            macOS: CrossPlatform.deviceName(),
                            watchOS: CrossPlatform.deviceName(),
                            tvOS: CrossPlatform.deviceName())
    var name: String

    @PlatformDependentValue(iOS: CrossPlatform.devicModel(),
                            macOS: CrossPlatform.devicModel(),
                            watchOS: CrossPlatform.devicModel(),
                            tvOS: CrossPlatform.devicModel())
    var model: String

    @PlatformDependentValue(iOS: CrossPlatform.systemVersion(),
                            macOS: CrossPlatform.systemVersion(),
                            watchOS: CrossPlatform.systemVersion(),
                            tvOS: CrossPlatform.systemVersion())
    var systemVersion: String

    @PlatformDependentValue(iOS: CrossPlatform.systemName(),
                            macOS: CrossPlatform.systemName(),
                            watchOS: CrossPlatform.systemName(),
                            tvOS: CrossPlatform.systemName())
    var systemName: String
}

let device = Device()

device.name
device.model
device.systemVersion
device.systemName

struct NumberContainer {
    @PlatformDependentValue(iOS: 1, macOS: 2, watchOS: 3, tvOS: 4)
    var number: Int
}

let nc = NumberContainer()
nc.number