additional safety for transactions by splitting between sync and async subclasses

HardcoreData/SynchronousDataTransaction.swift

@@ -0,0 +1,71 @@
+//
+//  SynchronousDataTransaction.swift
+//  HardcoreData
+//
+//  Created by John Rommel Estropia on 2015/02/28.
+//  Copyright (c) 2015 John Rommel Estropia. All rights reserved.
+//
+
+import Foundation
+import GCDKit
+
+public class SynchronousDataTransaction: DataTransaction {
+    
+    // MARK: Public
+    
+    /**
+    Saves the transaction changes and waits for completion synchronously. Note that this method should not be used after either the commit(_:) or commitAndWait() method was already called once.
+    
+    :returns: a SaveResult value indicating success or failure.
+    */
+    public func commitAndWait() {
+        
+        HardcoreData.assert(self.transactionQueue.isCurrentExecutionContext() == true, "Attempted to commit a \(self.dynamicType) outside a transaction queue.")
+        HardcoreData.assert(!self.isCommitted, "Attempted to commit a \(self.dynamicType) more than once.")
+        
+        self.isCommitted = true
+        self.result = self.context.saveSynchronously()
+    }
+    
+    /**
+    Begins a child transaction synchronously where NSManagedObject creates, updates, and deletes can be made.
+    
+    :param: closure the block where creates, updates, and deletes can be made to the transaction. Transaction blocks are executed serially in a background queue, and all changes are made from a concurrent NSManagedObjectContext.
+    :returns: a SaveResult value indicating success or failure, or nil if the transaction was not comitted synchronously
+    */
+    public func performTransactionAndWait(closure: (transaction: SynchronousDataTransaction) -> Void) -> SaveResult? {
+        
+        return SynchronousDataTransaction(
+            mainContext: self.context,
+            queue: self.childTransactionQueue,
+            closure: closure).performAndWait()
+    }
+    
+    
+    // MARK: Internal
+    
+    internal func performAndWait() -> SaveResult? {
+        
+        self.transactionQueue.sync {
+            
+            self.closure(transaction: self)
+            if !self.isCommitted {
+                
+                HardcoreData.log(.Warning, message: "The closure for the \(self.dynamicType) completed without being committed. All changes made within the transaction were discarded.")
+            }
+        }
+        return self.result
+    }
+    
+    internal init(mainContext: NSManagedObjectContext, queue: GCDQueue, closure: (transaction: SynchronousDataTransaction) -> Void) {
+        
+        self.closure = closure
+        
+        super.init(mainContext: mainContext, queue: queue)
+    }
+    
+    
+    // MARK: - Private
+    
+    private let closure: (transaction: SynchronousDataTransaction) -> Void
+}