How to implement Cora Data Persistent Management - ios

Question

I have the following structure so far:
- Singleton NetworkingManager (login, logout API calls)
- Subclass NSManagedObject (with son extension)
I don't know how to structure this part of the app?
Do I need a PersistentManager/global ObjectManagedContext?
Here are my classes:
NetworkingManager (API-call)
func getContacts() {
GET(APIURL.URL_CONTACTS ,parameters: nil,
{ (operation : NSURLSessionDataTask!, response : AnyObject!) -> Void in
var contacts = [Contacts]()
contacts <<<<* response
//_sharedPersistentManager.save(contacts!)
}, { (operation : NSURLSessionDataTask!, error : NSError!) -> Void in
println("Error contacts")
})
}
Model
import Foundation
import CoreData
class Contacts: NSManagedObject, Deserializable {
#NSManaged var firstname: String
#NSManaged var lastname: String
#NSManaged var id: String
required init(data: [String: AnyObject]) {
let managedContext = (UIApplication.sharedApplication().delegate
as AppDelegate).managedObjectContext!
let entity = NSEntityDescription.entityForName("Contacts", inManagedObjectContext: managedContext)!
super.init(entity: entity, insertIntoManagedObjectContext: managedContext)
self.id <<< data["id"]
self.firstname <<< data["1"]
self.lastname <<< data["2"]
}
}
This code fails... (Bad_ACCESS)
I struggle with the basic class design.
Would be so kind of you to post some pseudo-code and I can understand the basic concept.
All Tutorials explain how to save or fetch some data, but not a real concept for a whole app...
I'm looking for a basic concept like:
- You should implement one Persistent Manager Singleton class
//PersistentManager
- global ObjectManagedContext
- Singleton
- func save (model1: Model1)
- func save (model2: Model2)
- ....
//NetworkingManager
- Singleton
- ...
EDIT:
- added some code
- added further explanation

Answer 1

Typically your App would have one database (but it may have more than one, depending on your requirements). If we assume you only need one then you need to create a Core Data database (persistent store) and at a minimum one NSPersistentStoreCoordinator and one ManagedObjectContext in order to create and update database records via the ManagedObjects. Just use the template app to get sample code for doing this.
I would not try using the ManagedObjects init() method for creating the object, instead use a helper function in another class to do this. This init() method will get called automatically when you create the object so you might use it to set some default values for properties.
Below is an example ManagedObject (Swift class) and an Objective-C helper function. Apologies in advance, you will need to convert this to the equivalent Swift code.
//
// DocumentCategory.swift
// Sample
//
import Foundation
import CoreData
#objc(DocumentCategoryX)
class DocumentCategoryX: NSManagedObject {
#NSManaged var image: NSData
#NSManaged var name: String
#NSManaged var sortIndex: NSNumber
#NSManaged var viewName: String
#NSManaged var documents: NSSet
}
Sample helper function to create a managed object (a Core Data database record)
- (NSManagedObject*)createNewCategory:(NSString*)entityName sortIndex:(int)sortIndex withName:(NSString *)name viewName:(NSString *)viewName icon:(UIImage*)icon;
{
NSManagedObject *newCat = [NSEntityDescription
insertNewObjectForEntityForName:entityName
inManagedObjectContext:[self managedObjectContext]];
[newCat setValue:[NSNumber numberWithInt:sortIndex] forKey:#"sortIndex"];
[newCat setValue:name forKey:#"name"];
[newCat setValue:viewName forKey:#"viewName"];
[newCat setValue:UIImagePNGRepresentation(icon) forKey:#"image"]; // iOS
return newCat;
}
Swift function to save the MOC. Call this whenever you need to make sure things are written to disk.
// MARK: - Core Data Saving support
func saveContext () {
if let moc = self.managedObjectContext {
var error: NSError? = nil
if moc.hasChanges && !moc.save(&error) {
//FLOG("Unresolved error \(error), \(error!.userInfo)")
// Probably need a message to the user warning that a save failed!
}
}
}