How do I add offline-first caching and sync in Swift?

To implement offline-first caching and synchronization in a Swift application, you can utilize Core Data for local data storage and URLSession for syncing with a remote server. By caching data locally, your app can function without internet access while synchronizing changes when connectivity is restored.

Steps to Implement Offline-First Caching and Sync

  1. Set Up Core Data: Create your Core Data model to store your application data.
  2. Fetch Data from Core Data: Retrieve data from the local store first when the app launches.
  3. Network Request and Sync: Use URLSession to fetch data from your remote API.
  4. Update Core Data: Insert or update the local data store based on the fetched data.
  5. Handle Synchronization: Detect changes and sync data back to the remote server when connectivity is restored.

Example Code:

// Sample Swift code for fetching data and caching import UIKit import CoreData class DataManager { static let shared = DataManager() let context = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext func fetchData() { let request: NSFetchRequest = DataEntity.fetchRequest() do { let data = try context.fetch(request) // Use your data } catch { print("Failed to fetch data: \(error)") } } func syncData() { let url = URL(string: "https://api.yourservice.com/data")! let task = URLSession.shared.dataTask(with: url) { data, response, error in guard let data = data else { return } do { // Parse and update Core Data // Assume jsonData is the parsed dictionary let jsonData = try JSONSerialization.jsonObject(with: data, options: []) // Insert/Update Core Data } catch { print("Failed to parse or save data: \(error)") } } task.resume() } }

offline-first caching sync Swift Core Data data storage URLSession remote API

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