Day 10, I followed a tutorial on how to implement Core Data from scratch. Today, I will try to implement it into the existing app that I've been working on so far.
Things I want to accomplish
- Persisting data on app quit
Things I accomplished
- Adding Core Data to the app
Things I learned
Core Data is easier to add at the beginning of a project
When creating an iOS project, there is an option to add Core Data to the project. I chose no when starting this project because I did not want to overcomplicate the project. By adding it at the beginning, the AppDelegate.swift
file would have the following added for me:
// MARK: - Core Data stack
lazy var persistentContainer: NSPersistentContainer = {
/*
The persistent container for the application. This implementation
creates and returns a container, having loaded the store for the
application to it. This property is optional since there are legitimate
error conditions that could cause the creation of the store to fail.
*/
let container = NSPersistentContainer(name: "TodoList")
container.loadPersistentStores(completionHandler: { (storeDescription, error) in
if let error = error as NSError? {
// Replace this implementation with code to handle the error appropriately.
// fatalError() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
/*
Typical reasons for an error here include:
* The parent directory does not exist, cannot be created, or disallows writing.
* The persistent store is not accessible, due to permissions or data protection when the device is locked.
* The device is out of space.
* The store could not be migrated to the current model version.
Check the error message to determine what the actual problem was.
*/
fatalError("Unresolved error \(error), \(error.userInfo)")
}
})
return container
}()
// MARK: - Core Data Saving support
func saveContext () {
let context = persistentContainer.viewContext
if context.hasChanges {
do {
try context.save()
} catch {
// Replace this implementation with code to handle the error appropriately.
// fatalError() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
let nserror = error as NSError
fatalError("Unresolved error \(nserror), \(nserror.userInfo)")
}
}
}
These allow for TodoList.xcdatamodel
to be used in the app and to save information in Core Data.
Since I did not add Core Data when making the app initially, I had to add the variable and function into the AppDelegate.swift
file manually. To figure out what was there, I created a new application with Core Data and copied/pasted those into my current Xcode project.
If you have any questions about what I did or how I implemented anything, let me know! If you have any suggestions or other comments, let me know as well!
Top comments (2)
thank you
Any time!