ToyFS

AppDelegate.swift

import Cocoa

@NSApplicationMain
class AppDelegate: NSObject, NSApplicationDelegate {
    private lazy var toyFS: SimulatorFS = {
        return SimulatorFS()
    }()

    private lazy var userFileSystem: GMUserFileSystem  = {
        return GMUserFileSystem(delegate: self.toyFS, isThreadSafe: false)
    }()

    func applicationDidFinishLaunching(_ aNotification: Notification) {
        let options = ["native_xattr", "volname=ToyFS"]

        userFileSystem.mount(atPath: "/Volumes/loop", withOptions: options)
    }

    func applicationShouldTerminate(_ sender: NSApplication) -> NSApplication.TerminateReply {
        userFileSystem.unmount()
        return .terminateNow
    }
}

ToyFS.swift

import Foundation

final class ToyFS: NSObject {
    override class func attributesOfItem(atPath path: String!, userData: Any!) throws -> [AnyHashable : Any] {
        var attributes: [FileAttributeKey: Any] = [:]

        attributes[.creationDate] = Date()
        attributes[.modificationDate] = Date()
        attributes[.groupOwnerAccountID] = getgid()
        attributes[.ownerAccountID] = getuid()

        if path == "/" {
            attributes[.type] = FileAttributeType.typeDirectory
        } else {
            attributes[.type] = FileAttributeType.typeRegular
        }

        return attributes
    }

    override func contentsOfDirectory(atPath path: String!) throws -> [Any] {
        return ["file54", "file349"]
    }


    override func attributesOfFileSystem(forPath path: String!) throws -> [AnyHashable : Any] {
        var attributes: [FileAttributeKey: Any] = [:]
        attributes[FileAttributeKey(rawValue: kGMUserFileSystemVolumeSupportsExtendedDatesKey)] = true
        attributes[FileAttributeKey(rawValue: kGMUserFileSystemVolumeSupportsCaseSensitiveNamesKey)] = false

        return attributes
    }
}

Hi. I found your post on the OSXFUSE Google Group but I'm not able to reply to it. Did you ever end up making any further progress on this project? I might be trying to write my own Fuse FS in Swift in the near future and I'd love to have some more examples out there and/or access to someone's brain to pick.