/// If using CocoaPods
import CWCoreData

/// Tell the framework what your xcdatamodeld is called, if you forgot this the framework will raise an exception:
CoreDataStack.defaultStack.dataBaseName = "YOU_DATABASE_NAME"
CoreDataStack.defaultStack.sharedAppGroup = "YOU_SHARED_APP_CONTAINER_DOMAIN"

/// The main context, this is persisted across the app lifecycle:
let mainContext = CoreDataStack.defaultStack.mainQueueContext

/// Get a new private context:
let privateContext = CoreDataStack.privateQueueContext()

/// Get a new private context and specify a merge policy:
let privateContextWithPolicy = CoreDataStack.privateQueueContext(withMergePolicy: .errorMergePolicyType)

///Basic save:
CoreDataStack.defaultStack.save(context)

//Advanced save, allowing you to specifiy whether to performAndWait or simply perform:
CoreDataStack.defaultStack.save(context, performAndWait: false, completionHandler: { (result) in
print(result)
})

/// Create a new context to use for the insertion, we always use the 'privateQueueContext' to handle database changes. This will merge change back into the persistent store coordinator.
let context = CoreDataStack.privateQueueContext()

/// Create a new var to hold the event object:   
var newEvent : Event?

/// If we are running on iOS 10 then we can use the new API to insert:
if #available(iOS 10.0, *) {
    newEvent = Event(context: context)
} else {
    /// If we are using anything before iOS 10, then we use the helper method from the extension on NSManangedObject
    newEvent = Event.insertNewInstance(withContext: context) as? Event
}
                
/// If appropriate, configure the new managed object.
newEvent?.timestamp = NSDate()

/// We now save the changes, we can specify this with a completion block and whether we want to performBlockAndWait or just perform block:

/// Simply save:
CoreDataStack.defaultStack.save(context)

do {
            
    /// We use the main context for retrieval if we are going to use the obejct to populate the UI and we are NOT going to make direct changes to the object. Otherwise use the privateQeueContext.
    let context = CoreDataStack.defaultStack.mainQueueContext

    /// Create the predicate we will use:
    let predicate = NSPredicate(format: "timestamp < %@", NSDate())
    
    /// Get the event from the database if one exists with the provided predicate, there are other APIs that do similar operations with more options. See documentation.
    let savedEvent = try Event.fetchSingleObject(withPredicate: predicate, context: context, includesPendingChanges: true) as? Event

}
    
} catch {
    print("error")
}

/// Create a new context to use for the deletion, we always use the 'privateQueueContext' to handle database changes. This will merge change back into the persistent store coordinator.
let context = CoreDataStack.privateQueueContext()
            
let objectToDelete = /// Your Object...

/// Delete the object:
context.delete(objectToDelete)

/// Save the changes, we don't supply a completion handler here:
CoreDataStack.defaultStack.save(context)

/// Create a var for the fetched results controller:
var fetchedResultsController: NSFetchedResultsController<Event> {
    
    if _fetchedResultsController != nil {
        return _fetchedResultsController!
    }
    
    /// Create the fetch request:
    let fetchRequest: NSFetchRequest<Event> = Event.fetchRequest()
    
    /// Optional: Set the batch size to a suitable number. 
    fetchRequest.fetchBatchSize = 20
    
    // Edit the sort key as appropriate.
    let sortDescriptor = NSSortDescriptor(key: "timestamp", ascending: false)
    
    fetchRequest.sortDescriptors = [sortDescriptor]
    
    /// Edit the section name key path and cache name if appropriate.
    /// nil for section name key path means "no sections".
    /// We always use the mainQueueContext for FetchedResultsControllers and any other time where we need the UI to be populated from the database object:
    let aFetchedResultsController = NSFetchedResultsController(fetchRequest: fetchRequest, managedObjectContext: CoreDataStack.defaultStack.mainQueueContext, sectionNameKeyPath: nil, cacheName: nil)
    aFetchedResultsController.delegate = self
    _fetchedResultsController = aFetchedResultsController
    
    do {
        try _fetchedResultsController!.performFetch()
    } catch {
        print(error)
    }
    
    return _fetchedResultsController!
}

var _fetchedResultsController: NSFetchedResultsController<Event>? = nil