PersistentDataStore+Storing.swift

typealias Identifier = String

enum Result {
    case failed(Error)
    case noData
    case success(Identifier)
}
    
func storeData(_ dataProvider: @escaping () -> (Data?), identifier: Identifier = UUID().uuidString, completionHandler block: @escaping (Result) -> ()) {
    queue.async(flags: .barrier) {
        let url = self.url(forIdentifier: identifier)
        guard let data = dataProvider(), !data.isEmpty else {
            DispatchQueue.main.async {
                block(.noData)
            }
            return
        }
        do {
            try data.write(to: url, options: .atomic)
            DispatchQueue.main.async {
                block(.success(identifier))
            }
        }
        catch {
            DispatchQueue.main.async {
                block(.failed(error))
            }
        }
    }
}

// Example (adding data to data store with unique identifier):
persistentStore.storeData({ () -> (Data?) in
    return image.jpegData(compressionQuality: 1.0)
}) { (result) in
    switch result {
    case .success(let identifier):
        print("Stored data successfully with identifier \(identifier).")
    case .noData:
        print("No data to store.")
    case .failed(let error):
        print("Failed storing data with error \(error)")
    }
}