SkipFoundation

Foundation support for Skip apps.

See what API is currently implemented here.

About

SkipFoundation vends the skip.foundation Kotlin package. It is a reimplementation of Foundation for Kotlin on Android. Its goal is to mirror as much of Foundation as possible, allowing Skip developers to use Foundation API with confidence.

SkipFoundation also implements portions of the CryptoKit API.

Dependencies

SkipFoundation depends on the skip transpiler plugin as well as the SkipLib package.

SkipFoundation is part of the core SkipStack and is not intended to be imported directly. The module is transparently adopted through the translation of import Foundation into import skip.foundation.* by the Skip transpiler.

Android Libraries

• SkipFoundation includes source code from the UrlEncoderUtil library to implement percent escaping.

Status

SkipFoundation supports many of the Foundation framework's most common APIs, but there are many more that are not yet ported. See Foundation Support.

When you want to use a Foundation API that has not been implemented, you have options. You can try to find a workaround using only supported API, embed Kotlin code directly as described in the Skip docs, or add support to SkipFoundation. If you choose to enhance SkipFoundation itself, please consider contributing your code back for inclusion in the official release.

Contributing

We welcome contributions to SkipFoundation. The Skip product documentation includes helpful instructions and tips on local Skip library development.

The most pressing need is to implement more of the most-used Foundation APIs. To help fill in unimplemented API in SkipFoundation:

1. Find unimplemented API.
2. Write an appropriate Kotlin implementation. See Implementation Strategy below.
3. Edit the corresponding tests to make sure they are no longer skipped, and that they pass. If there aren't existing tests, write some. See Tests.
4. Submit a PR.

Other forms of contributions such as test cases, comments, and documentation are also welcome!

Implementation Strategy

The goal of SkipFoundation is to mirror the Foundation framework for Android. When possible, SkipFoundation types wrap corresponding Kotlin or Java foundation types. When a SkipFoundation type wraps a corresponding Kotlin or Java type, please conform to the skip.lib.KotlinConverting<T> protocol, which means adding a .kotlin() function:

#if SKIP
extension Calendar: KotlinConverting<java.util.Calendar> {
    public override func kotlin(nocopy: Bool = false) -> java.util.Calendar {
        return nocopy ? platformValue : platformValue.clone() as java.util.Calendar
    }
}
#endif

You should also implement a constructor that accepts the equivalent Kotlin or Java object.

Tests

SkipFoundation's Tests/ folder contains the entire set of official Foundation framework test cases. Through the magic of SkipUnit, this allows us to validate our SkipFoundation API implementations on Android against the same test suite used by the Foundation team on iOS.

It is SkipFoundation's goal to include - and pass - as much of the official test suite as possible.

Foundation Support

The following table summarizes SkipFoundation's Foundation API support on Android. Anything not listed here is likely not supported. Note that in your iOS-only code - i.e. code within #if !SKIP blocks - you can use any Foundation API you want.

Support levels:

• ✅ – Full
• 🟢 – High
• 🟡 – Medium
• 🟠 – Low

Support	API
🟡	Bundle static var main: Bundle static var module: Bundle init?(path: String) init?(url: URL) init(for forClass: AnyClass) init() var bundleURL: URL var resourceURL: URL? var bundlePath: String var resourcePath: String? func url(forResource: String? = nil, withExtension: String? = nil, subdirectory: String? = nil, localization: String? = nil) -> URL? func path(forResource: String? = nil, ofType: String? = nil, inDirectory: String? = nil, forLocalization: String? = nil) -> String? var developmentLocalization: String var localizations: [String] func localizedString(forKey key: String, value: String?, table tableName: String?) -> String var localizations: [String]
🟡	Calendar Only .gregorian and .iso8601 identifiers are supported init(identifier: Calendar.Identifier) static var current: Calendar var locale: Locale var timeZone: TimeZone var identifier: Calendar.Identifier var eraSymbols: [String] var monthSymbols: [String] var shortMonthSymbols: [String] var weekdaySymbols: [String] var shortWeekdaySymbols: [String] var amSymbol: String var pmSymbol: String func date(from components: DateComponents) -> Date? func dateComponents(in zone: TimeZone? = nil, from date: Date) -> DateComponents func dateComponents(_ components: Set<Calendar.Component>, from start: Date, to end: Date) -> DateComponents func dateComponents(_ components: Set<Calendar.Component>, from date: Date) -> DateComponents func date(byAdding components: DateComponents, to date: Date, wrappingComponents: Bool = false) -> Date? func date(byAdding component: Calendar.Component, value: Int, to date: Date, wrappingComponents: Bool = false) -> Date? func isDateInWeekend(_ date: Date) -> Bool
🟠	CharacterSet Vended character sets are not complete static var whitespaces: CharacterSet static var whitespacesAndNewlines: CharacterSet static var newlines: CharacterSet static var urlHostAllowed: CharacterSet static var urlFragmentAllowed: CharacterSet static var urlPathAllowed: CharacterSet static var urlQueryAllowed: CharacterSet init() func insert(_ character: Unicode.Scalar) -> (inserted: Bool, memberAfterInsert: Unicode.Scalar) func update(with character: Unicode.Scalar) -> Unicode.Scalar? func remove(_ character: Unicode.Scalar) -> Unicode.Scalar? func contains(_ member: Unicode.Scalar) -> Bool func union(_ other: CharacterSet) -> CharacterSet mutating func formUnion(_ other: CharacterSet) func intersection(_ other: CharacterSet) -> CharacterSet mutating func formIntersection(_ other: CharacterSet) func subtracting(_ other: CharacterSet) mutating func subtract(_ other: CharacterSet) func symmetricDifference(_ other: CharacterSet) -> CharacterSet mutating func formSymmetricDifference(_ other: CharacterSet) func isSuperset(of other: CharacterSet) -> Bool func isSubset(of other: CharacterSet) -> Bool func isDisjoint(with other: CharacterSet) -> Bool func isStrictSubset(of other: CharacterSet) -> Bool func isStrictSuperset(of other: CharacterSet) -> Bool var isEmpty: Bool
✅	CocoaError
✅	ComparisonResult
🟠	CryptoKit See the CryptoKit topic for details on supported API.
✅	CustomNSError
🟡	Data Data does not conform to Collection protocols init() init(count: Int) init(capacity: Int) init(_ data: Data) init(_ bytes: [UInt8], length: Int? = nil) init(_ checksum: Digest) init?(base64Encoded: String, options: Data.Base64DecodingOptions = []) init(contentsOfFile filePath: String) throws init(contentsOf url: URL, options: Data.ReadingOptions = []) var count: Int var isEmpty: Bool var bytes: [UInt8] var utf8String: String? func base64EncodedString() -> String func sha256() -> Data func hex() -> String mutating func reserveCapacity(_ minimumCapacity: Int) mutating func append(_ other: Data) mutating func append(contentsOf bytes: [UInt8]) mutating func append(contentsOf data: Data) subscript(index: Int) -> UInt8 func write(to url: URL, options: Data.WritingOptions = []) throws
🟡	Date Formatting functions not supported with the exception of: func ISO8601Format(_ style: Date.ISO8601FormatStyle = .iso8601) -> String
🟢	DateComponents nanosecond, weekdayOrdinal, quarter, yearForWeekOfYear are not supported
🟡	DateFormatter var dateStyle: DateFormatter.Style var timeStyle: DateFormatter.Style var isLenient: Bool var dateFormat: String func setLocalizedDateFormatFromTemplate(dateFormatTemplate: String) static func dateFormat(fromTemplate: String, options: Int, locale: Locale?) -> String? static func localizedString(from date: Date, dateStyle: DateFormatter.Style, timeStyle: DateFormatter.Style) -> String var timeZone: TimeZone? var locale: Locale? var calendar: Calendar? func date(from string: String) -> Date? func string(from date: Date) -> String func string(for obj: Any?) -> String?
✅	DateInterval
🟠	Decimal Aliased to java.math.BigDecimal
🟠	DispatchQueue static let main: DispatchQueue func async(execute: () -> Void) func asyncAfter(deadline: DispatchTime, execute: () -> Void) func asyncAfter(wallDeadline: DispatchWallTime, execute: () -> Void)
🟢	FileManager static let `default`: FileManager let temporaryDirectory: URL let currentDirectoryPath: String func createSymbolicLink(at url: URL, withDestinationURL destinationURL: URL) throws func createSymbolicLink(atPath path: String, withDestinationPath destinationPath: String) throws func createDirectory(at url: URL, withIntermediateDirectories: Bool, attributes: [FileAttributeKey : Any]? = nil) throws func createDirectory(atPath path: String, withIntermediateDirectories: Bool, attributes: [FileAttributeKey : Any]? = nil) throws func destinationOfSymbolicLink(atPath path: String) throws func attributesOfItem(atPath path: String) throws -> [FileAttributeKey: Any] func setAttributes(_ attributes: [FileAttributeKey : Any], ofItemAtPath path: String) throws func createFile(atPath path: String, contents: Data? = nil, attributes: [FileAttributeKey : Any]? = nil) -> Bool func copyItem(atPath path: String, toPath: String) throws func copyItem(at url: URL, to: URL) throws func moveItem(atPath path: String, toPath: String) throws func moveItem(at path: URL, to: URL) throws func subpathsOfDirectory(atPath path: String) throws -> [String] func subpaths(atPath path: String) -> [String]? func removeItem(atPath path: String) throws func removeItem(at url: URL) throws func fileExists(atPath path: String) -> Bool func isReadableFile(atPath path: String) -> Bool func isExecutableFile(atPath path: String) -> Bool func isDeletableFile(atPath path: String) -> Bool func isWritableFile(atPath path: String) -> Bool func contentsOfDirectory(at url: URL, includingPropertiesForKeys: [URLResourceKey]?) throws -> [URL] func contentsOfDirectory(atPath path: String) throws -> [String] func url(for directory: FileManager.SearchPathDirectory, in domain: FileManager.SearchPathDomainMask, appropriateFor url: URL?, create shouldCreate: Bool) throws -> URL
✅	HTTPURLResponse
🟢	IndexPath Cannot assign from an array literal Cannot assign to a range subscript
🟡	IndexSet This is an inefficient implementation using an internal Set init(integersIn range: any RangeExpression<Int>) init(integer: Int) init() func integerGreaterThan(_ integer: Int) -> Int? func integerLessThan(_ integer: Int) -> Int? func integerGreaterThanOrEqualTo(_ integer: Int) -> Int? func integerLessThanOrEqualTo(_ integer: Int) -> Int? func count(in range: any RangeExpression<Int>) -> Int func contains(integersIn range: any RangeExpression<Int>) -> Bool func contains(integersIn indexSet: IntSet) -> Bool func intersects(integersIn range: any RangeExpression<Int>) -> Bool mutating func insert(integersIn range: any RangeExpression<Int>) mutating func remove(integersIn range: any RangeExpression<Int>) func filteredIndexSet(in range: any RangeExpression<Int>, includeInteger: (Int) throws -> Bool) rethrows -> IndexSet func filteredIndexSet(includeInteger: (Int) throws -> Bool) rethrows -> IndexSet Supports the full SetAlgebra protocol
🟡	ISO8601DateFormatter static func string(from date: Date, timeZone: TimeZone) -> String var timeZone: TimeZone? func date(from string: String) -> Date? func string(from date: Date) -> String func string(for obj: Any?) -> String?
🟢	JSONDecoder Snake case key decoding is not supported
🟢	JSONEncoder Snake case key encoding is not supported
✅	JSONSerialization
✅	Locale
✅	LocalizedError
✅	LocalizedStringResource
✅	Logger
✅	Notification
🟡	NotificationCenter static let default: NotificationCenter func addObserver(forName name: Notification.Name?, object: Any?, queue: OperationQueue?, using block: (Notification) -> Void) -> Any func removeObserver(_ observer: Any) func post(_ notification: Notification) func post(name: Notification.Name, object: Any?, userInfo: [AnyHashable: Any]? = nil) func notifications(named: Notification.Name, object: AnyObject? = nil) -> Notifications Also see support for NotificationCenter.publisher in the SkipModel module
✅	NSError
✅	NSLock
✅	NSLocalizedString
✅	NSRecursiveLock
🟢	Number init(value: Int8) init(value: Int16) init(value: Int32) init(value: Int64) init(value: UInt8) init(value: UInt16) init(value: UInt32) init(value: UInt64) init(value: Float) init(value: Double) init(_ value: Int8) init(_ value: Int16) init(_ value: Int32) init(_ value: Int64) init(_ value: UInt8) init(_ value: UInt16) init(_ value: UInt32) init(_ value: UInt64) init(_ value: Float) init(_ value: Double) var doubleValue: Double var intValue: Int var longValue: Int64 var int64Value: Int64 var int32Value: Int32 var int16Value: Int16 var int8Value: Int8
🟢	NumberFormatter The following styles are supported: .none, .decimal, .currency, .percent var numberStyle: NumberFormatter.Style var locale: Locale? var format: String var groupingSize: Int var generatesDecimalNumbers: Bool var alwaysShowsDecimalSeparator: Bool var usesGroupingSeparator: Bool var multiplier: NSNumber? var groupingSeparator: String? var percentSymbol: String? var currencySymbol: String? var zeroSymbol: String? var minusSign: String? var exponentSymbol: String? var negativeInfinitySymbol: String var positiveInfinitySymbol: String var internationalCurrencySymbol: String? var decimalSeparator: String? var currencyCode: String? var currencyDecimalSeparator: String? var notANumberSymbol: String? var positiveSuffix: String? var negativeSuffix: String? var positivePrefix: String? var negativePrefix: String? var maximumFractionDigits: Int var minimumFractionDigits: Int var maximumIntegerDigits: Int var minimumIntegerDigits: Int func string(from number: NSNumber) -> String? func string(from number: Int) -> String? func string(for object: Any?) -> String? func number(from string: String) -> NSNumber?
🟠	OperationQueue static let main: OperationQueue
🟢	OSAllocatedUnfairLock init() init(initialState: State) init(uncheckedState initialState: State) func lock() func unlock() func lockIfAvailable() -> Bool func withLockUnchecked<R>(_ body: (inout State) throws -> R) rethrows -> R func func withLockUnchecked<R>(_ body: () throws -> R) rethrows -> R func withLock<R>(_ body: (inout State) throws -> R) rethrows -> R func withLock<R>(_ body: () throws -> R) rethrows -> R func withLockIfAvailableUnchecked<R>(_ body: (inout State) throws -> R) rethrows -> R? func withLockIfAvailableUnchecked<R>(_ body: () throws -> R) rethrows -> R? func withLockIfAvailable<R>(_ body: @Sendable (inout State) throws -> R) rethrows -> R? func withLockIfAvailable<R>(_ body: () throws -> R) rethrows -> R?
✅	POSIXError
🟡	ProcessInfo static let processInfo: ProcessInfo var globallyUniqueString: String var systemProperties: [String: String] var environment: [String : String] var processIdentifier: Int32 var arguments: [String] var hostName: String var processorCount: Int var operatingSystemVersionString: String var isMacCatalystApp: Bool var isiOSAppOnMac: Bool
🟠	PropertyListSerialization static func propertyList(from: Data, options: PropertyListSerialization.ReadOptions = [], format: Any?) throws -> [String: String]? Ignores any given options and format
🟠	RunLoop static let main: RunLoop
✅	RecoverableError
🟢	String Core String API is defined in SkipLib. These extensions are defined in SkipFoundation init(data: Data, encoding: StringEncoding) init(bytes: [UInt8], encoding: StringEncoding) init(contentsOf: URL) var capitalized: String var deletingLastPathComponent: String func replacingOccurrences(of search: String, with replacement: String) -> String func components(separatedBy separator: String) -> [String] func trimmingCharacters(in set: CharacterSet) -> String func addingPercentEncoding(withAllowedCharacters: CharacterSet) -> String? var removingPercentEncoding: String? var utf8Data: Data var utf8: [UInt8] var utf16: [UInt8] var utf32: [UInt8] var unicodeScalars: [UInt8] func data(using: StringEncoding, allowLossyConversion: Bool = true) -> Data? func write(to url: URL, atomically useAuxiliaryFile: Bool, encoding enc: StringEncoding) throws func write(toFile path: String, atomically useAuxiliaryFile: Bool, encoding enc: StringEncoding) throws
✅	StringLocalizationValue
✅	func strlen(_ string: String) -> Int
✅	func strncmp(_ str1: String, _ str2: String) -> Int
🟡	Timer init(timeInterval: TimeInterval, repeats: Bool, block: (Timer) -> Void) static func scheduledTimer(withTimeInterval interval: TimeInterval, repeats: Bool, block: (Timer) -> Void) -> Timer var timeInterval: TimeInterval func invalidate() var isValid: Bool var userInfo: Any? Also see support for Timer.publish in the SkipModel module
🟢	TimeZone static var current: TimeZone static var autoupdatingCurrent: TimeZone static var `default`: TimeZone static var system: TimeZone static var local: TimeZone static var gmt: TimeZone init?(identifier: String) init?(abbreviation: String) init?(secondsFromGMT seconds: Int) var identifier: String func abbreviation(for date: Date = Date()) -> String? func secondsFromGMT(for date: Date = Date()) -> Int func isDaylightSavingTime(for date: Date = Date()) -> Bool func daylightSavingTimeOffset(for date: Date = Date()) -> TimeInterval var nextDaylightSavingTimeTransition: Date? func nextDaylightSavingTimeTransition(after date: Date) -> Date? static var knownTimeZoneIdentifiers: [String] static var knownTimeZoneNames: [String] static var abbreviationDictionary: [String : String] func localizedName(for style: NameStyle, locale: Locale?) -> String?
✅	UnknownNSError
🟢	URL init(_ url: URL) init?(string: String, relativeTo baseURL: URL? = nil) init(fileURLWithPath path: String, isDirectory: Bool? = nil, relativeTo base: URL? = nil) static func currentDirectory() -> URL static var homeDirectory: URL static var temporaryDirectory: URL static var cachesDirectory: URL static var documentsDirectory: URL let baseURL: URL? var scheme: String? var host: String? func host(percentEncoded: Bool = true) -> String? var port: Int? var path: String? func path(percentEncoded: Bool = true) -> String? var hasDirectoryPath: Bool var query: String? func query(percentEncoded: Bool = true) -> String? var fragment: String? func fragment(percentEncoded: Bool = true) -> String? var standardized: URL var standardizedFileURL: URL mutating func standardize() var absoluteURL: URL var absoluteString: String var relativePath: String var relativeString: String var pathComponents: [String] var lastPathComponent: String var pathExtension: String var isFileURL: Bool func appendingPathComponent(_ pathComponent: String) -> URL mutating func appendPathComponent(_ pathComponent: String) func appendingPathComponent(_ pathComponent: String, isDirectory: Bool) -> URL mutating func appendPathComponent(_ pathComponent: String, isDirectory: Bool) func appendingPathExtension(_ pathExtension: String) -> URL mutating func appendPathExtension(_ pathExtension: String) func deletingLastPathComponent() -> URL mutating func deleteLastPathComponent() -> URL func deletingPathExtension() -> URL mutating func deletePathExtension() func resolvingSymlinksInPath() -> URL mutating func resolveSymlinksInPath() -> URL func checkResourceIsReachable() throws -> Bool
✅	URLError
✅	URLQueryItem
🟡	URLRequest Many properties are currently ignored by URLSession httpBodyStream is not supported
✅	URLResponse
🟡	URLSession static let shared: URLSession init(configuration: URLSessionConfiguration, delegate: URLSessionDelegate? = nil, delegateQueue: OperationQueue? = nil) var configuration: URLSessionConfiguration var sessionDescription: String? var delegate: URLSessionDelegate? var delegateQueue: OperationQueue? func data(for request: URLRequest, delegate: URLSessionTaskDelegate? = nil) async throws -> (Data, URLResponse) func data(from url: URL, delegate: URLSessionTaskDelegate? = nil) async throws -> (Data, URLResponse) func upload(for request: URLRequest, fromFile fileURL: URL, delegate: URLSessionTaskDelegate? = nil) async throws -> (Data, URLResponse) func upload(for request: URLRequest, from bodyData: Data, delegate: URLSessionTaskDelegate? = nil) async throws -> (Data, URLResponse) func bytes(for request: URLRequest, delegate: URLSessionTaskDelegate? = nil) async throws -> (AsyncBytes, URLResponse) func bytes(from url: URL, delegate: URLSessionTaskDelegate? = nil) async throws -> (AsyncBytes, URLResponse) func dataTask(with url: URL, completionHandler: ((Data?, URLResponse?, Error?) -> Void)? = nil) -> URLSessionDataTask func dataTask(with request: URLRequest, completionHandler: ((Data?, URLResponse?, Error?) -> Void)? = nil) -> URLSessionDataTask func uploadTask(with: URLRequest, from: Data?, completionHandler: ((Data?, URLResponse?, Error?) -> Void)? = nil) -> URLSessionUploadTask func uploadTask(with: URLRequest, fromFile: URL, completionHandler: ((Data?, URLResponse?, Error?) -> Void)?) -> URLSessionUploadTask func webSocketTask(with url: URL) -> URLSessionWebSocketTask func webSocketTask(with request: URLRequest) -> URLSessionWebSocketTask func webSocketTask(with url: URL, protocols: [String]) -> URLSessionWebSocketTask func finishTasksAndInvalidate() func getTasksWithCompletionHandler(_ handler: ([URLSessionDataTask], [URLSessionUploadTask], [URLSessionDownloadTask]) -> Void) var tasks: ([URLSessionDataTask], [URLSessionUploadTask], [URLSessionDownloadTask]) func getAllTasks(handler: ([URLSessionTask]) -> Void) var allTasks: [URLSessionTask] func invalidateAndCancel() struct AsyncBytes: AsyncSequence
🟡	URLSessionConfiguration Many properties are currently ignored by URLSession
🟢	URLSessionDataTask static let defaultPriority: Float static let lowPriority: Float static let highPriority: Float var taskIdentifier: Int var taskDescription: String? var originalRequest: URLRequest? var delegate: URLSessionTaskDelegate? var state: URLSessionTask.State var error: Error? var priority: Float func suspend() func resume() func cancel()
🟢	URLSessionUploadTask static let defaultPriority: Float static let lowPriority: Float static let highPriority: Float var taskIdentifier: Int var taskDescription: String? var originalRequest: URLRequest? var delegate: URLSessionTaskDelegate? var state: URLSessionTask.State var error: Error? var priority: Float func suspend() func resume() func cancel()
🟢	URLSessionWebSocketTask static let defaultPriority: Float static let lowPriority: Float static let highPriority: Float var taskIdentifier: Int var taskDescription: String? var originalRequest: URLRequest? var delegate: URLSessionTaskDelegate? var state: URLSessionTask.State var error: Error? var priority: Float func suspend() func resume() func cancel() func cancel(with closeCode: CloseCode, reason: Data?) var maximumMessageSize: Int var closeCode: CloseCode var closeReason: Data? func send(_ message: Message) async throws -> Void func receive() async throws -> Message
🟢	UserDefaults static var standard: UserDefaults init(suiteName: String?) func register(defaults registrationDictionary: [String : Any]) func set(_ value: Int, forKey defaultName: String) func set(_ value: Boolean, forKey defaultName: String) func set(_ value: Double, forKey defaultName: String) func set(_ value: String, forKey defaultName: String) func set(_ value: Any?, forKey defaultName: String) func removeObject(forKey defaultName: String) func object(forKey defaultName: String) -> Any? func string(forKey defaultName: String) -> String? func double(forKey defaultName: String) -> Double? func integer(forKey defaultName: String) -> Int? func bool(forKey defaultName: String) -> Bool? func url(forKey defaultName: String) -> URL? func data(forKey defaultName: String) -> Data? func dictionaryRepresentation() -> [String : Any] Array and dictionary values are not supported
🟢	UUID init() init?(uuidString: String) static func fromString(uuidString: String) -> UUID? var uuidString: String

Topics

CryptoKit

SkipFoundation vends portions of the CryptoKit framework by delegating to the built-in Java implementations:

• SHA256
• SHA256Digest
• SHA384
• SHA384Digest
• SHA512
• SHA512Digest
• Insecure.MD5
• Insecure.MD5Digest
• Insecure.SHA1
• Insecure.SHA1Digest
• HMACMD5
• HMACSHA1
• HMACSHA256
• HMACSHA384
• HMACSHA512

Each supported algorithm includes the following API:

associatedtype Digest
    
public static func hash(data: Data) -> Digest
public func update(_ data: DataProtocol)
public func finalize() -> Digest

The returned Digest in turn acts as a sequence of UInt8 bytes.

Files

Skip implements much of Foundation.FileManager, which should be the primary interface for interacting with the file system.

The app-specific folder can be accessed like:

// on Android, this is Context.getFilesDir()
let folder = try FileManager.default.url(for: FileManager.SearchPathDirectory.documentDirectory, in: FileManager.SearchPathDomainMask.userDomainMask, appropriateFor: nil, create: false)

And to read and write to the cache folders:

// on Android, this is Context.getCachesDir()
let caches = try FileManager.default.url(for: FileManager.SearchPathDirectory.cachesDirectory, in: FileManager.SearchPathDomainMask.userDomainMask, appropriateFor: nil, create: false)

And the system temporary folder can be accessed with:

let tmpdir = NSTemporaryDirectory()

None of the other FileManager.SearchPathDirectory enumerations are implemented in Skip.

Both Data and String have the ability to read and write to and from URLs and path strings.