CoreStore/Sources/Internal/NSManagedObjectContext+Setup.swift

//
//  NSManagedObjectContext+Setup.swift
//  CoreStore
//
//  Copyright © 2015 John Rommel Estropia
//
//  Permission is hereby granted, free of charge, to any person obtaining a copy
//  of this software and associated documentation files (the "Software"), to deal
//  in the Software without restriction, including without limitation the rights
//  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
//  copies of the Software, and to permit persons to whom the Software is
//  furnished to do so, subject to the following conditions:
//
//  The above copyright notice and this permission notice shall be included in all
//  copies or substantial portions of the Software.
//
//  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
//  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
//  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
//  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
//  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
//  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
//  SOFTWARE.
//

import Foundation
import CoreData


// MARK: - NSManagedObjectContext

internal extension NSManagedObjectContext {
    
    // MARK: Internal
    
    @nonobjc
    internal weak var parentStack: DataStack? {
        
        get {
            
            if let parentContext = self.parentContext {
                
                return parentContext.parentStack
            }
            
            return getAssociatedObjectForKey(&PropertyKeys.parentStack, inObject: self)
        }
        set {
            
            guard self.parentContext == nil else {
                
                return
            }
            
            setAssociatedWeakObject(
                newValue,
                forKey: &PropertyKeys.parentStack,
                inObject: self
            )
        }
    }
    
    @nonobjc
    internal static func rootSavingContextForCoordinator(coordinator: NSPersistentStoreCoordinator) -> NSManagedObjectContext {
        
        let context = NSManagedObjectContext(concurrencyType: .PrivateQueueConcurrencyType)
        context.persistentStoreCoordinator = coordinator
        context.mergePolicy = NSMergeByPropertyObjectTrumpMergePolicy
        context.undoManager = nil
        context.setupForCoreStoreWithContextName("com.corestore.rootcontext")
        
        return context
    }
    
    @nonobjc
    internal static func mainContextForRootContext(rootContext: NSManagedObjectContext) -> NSManagedObjectContext {
        
        let context = NSManagedObjectContext(concurrencyType: .MainQueueConcurrencyType)
        context.parentContext = rootContext
        context.mergePolicy = NSRollbackMergePolicy
        context.undoManager = nil
        context.setupForCoreStoreWithContextName("com.corestore.maincontext")
        context.observerForDidSaveNotification = NotificationObserver(
            notificationName: NSManagedObjectContextDidSaveNotification,
            object: rootContext,
            closure: { [weak context] (note) -> Void in
                
                context?.performBlock { () -> Void in
                    
                    let updatedObjects = (note.userInfo?[NSUpdatedObjectsKey] as? Set<NSManagedObject>) ?? []
                    for object in updatedObjects {
                        
                        context?.objectWithID(object.objectID).willAccessValueForKey(nil)
                    }
                    context?.mergeChangesFromContextDidSaveNotification(note)
                }
            }
        )
        
        return context
    }
    
    
    // MARK: Private
    
    private struct PropertyKeys {
        
        static var parentStack: Void?
        static var observerForDidSaveNotification: Void?
    }
    
    @nonobjc
    private var observerForDidSaveNotification: NotificationObserver? {
        
        get {
            
            return getAssociatedObjectForKey(
                &PropertyKeys.observerForDidSaveNotification,
                inObject: self
            )
        }
        set {
            
            setAssociatedRetainedObject(
                newValue,
                forKey: &PropertyKeys.observerForDidSaveNotification,
                inObject: self
            )
        }
    }
}