FileManagerによるファイル操作でCombineを使う。

FileManagerExtensions.swift

import Foundation
import Combine

extension FileManager {
    struct RemoveItemPublisher: Publisher {
        typealias Output = Void
        typealias Failure = Error
        
        var url: URL
        var fileManager: FileManager
        init(at url: URL, fileManager: FileManager) {
            self.url = url
            self.fileManager = fileManager
        }
        
        func receive<S>(
            subscriber: S
        ) where S : Subscriber, Failure == S.Failure, Output == S.Input {
            Deferred {
                Future { [self] promise in
                    do {
                        try fileManager.removeItem(at: url)
                        promise(.success(()))
                    } catch {
                        promise(.failure(error))
                    }
                }
            }
            .receive(subscriber: subscriber)
        }
        
        func ignoreNoSuchFile() -> AnyPublisher<Void, Error> {
            tryCatch { (error) -> AnyPublisher<Void, Error> in
                let nserror = error as NSError
                guard nserror.domain == NSCocoaErrorDomain,
                      CocoaError.Code(rawValue: nserror.code) == .fileNoSuchFile
                else {
                    throw error
                }
                return Just(()).setFailureType(to: Error.self).eraseToAnyPublisher()
            }
            .eraseToAnyPublisher()
        }
    }
    
    func removeItemPublisher(at url: URL) -> RemoveItemPublisher {
        RemoveItemPublisher(at: url, fileManager: self)
    }
    
    func copyItemPublisher(at srcURL: URL, to dstURL: URL) -> AnyPublisher<Void, Error> {
        Deferred {
            Future { [self] promise in
                do {
                    try copyItem(at: srcURL, to: dstURL)
                    promise(.success(()))
                } catch {
                    promise(.failure(error))
                }
            }
        }
        .eraseToAnyPublisher()
    }
    
    func mergeItemsPublisher(at srcURLs: [URL], to dstURL: URL) -> AnyPublisher<Void, Error> {
        Deferred {
            Future { promise in
                do {
                    try Data().write(to: dstURL)
                    let fileHandle = try FileHandle(forWritingTo: dstURL)
                    try srcURLs
                        .map { try Data(contentsOf: $0, options: .mappedIfSafe) }
                        .forEach { fileHandle.write($0) }
                    try fileHandle.close()
                    promise(.success(()))
                } catch {
                    promise(.failure(error))
                }
            }
        }
        .eraseToAnyPublisher()
    }
}