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PONSUndoManager undo Not Working With Core Data
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  1. PONSUndoManager undo Not Working With Core Data
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    copied!<p>I am trying to create an iPhone application where the user can add entries. When he presses a new entry, a box will popup asking him for some information. Then he can either press "Cancel" or "Save" to discard the data or save it to disk.</p> <p>For saving, I am using the Core Data framework, which works pretty well. However, I cannot get the "Cancel" button to work. When the window pops up, asking for information, I create a new object in the managed object context (MOC). Then when the user presses cancel, I try to use the NSUndoManager belonging to the MOC.</p> <p>I would also like to do it using nested undo groups, because there might be nested groups. </p> <p>To test this, I wrote a simple application. The application is just the "Window based application" template with Core Data enabled. For the Core Data model, I create a single entity called "Entity" with integer attribute "x". Then inside the applicationDidFinishLaunching, I add this code:</p> <pre><code>- (void)applicationDidFinishLaunching:(UIApplication *)application { // Override point for customization after app launch unsigned int x=arc4random()%1000; [self.managedObjectContext processPendingChanges]; [self.managedObjectContext.undoManager beginUndoGrouping]; NSManagedObject *entity=[NSEntityDescription insertNewObjectForEntityForName:@"Entity" inManagedObjectContext:self.managedObjectContext]; [entity setValue:[NSNumber numberWithInt:x] forKey:@"x"]; NSLog(@"Insert Value %d",x); [self.managedObjectContext processPendingChanges]; [self.managedObjectContext.undoManager endUndoGrouping]; [self.managedObjectContext.undoManager undoNestedGroup]; NSFetchRequest *fetchRequest=[[NSFetchRequest alloc] init]; NSEntityDescription *entityEntity=[NSEntityDescription entityForName:@"Entity" inManagedObjectContext:self.managedObjectContext]; [fetchRequest setEntity:entityEntity]; NSArray *result=[self.managedObjectContext executeFetchRequest:fetchRequest error:nil]; for(entity in result) { NSLog(@"FETCHED ENTITY %d",[[entity valueForKey:@"x"] intValue]); } [window makeKeyAndVisible]; } </code></pre> <p>The idea is simple. Try to insert a new Entity object, undo it, fetch all Entity objects in the MOC and print them out. If everything worked correctly, there should be no objects at the end.</p> <p>However, I get this output:</p> <pre><code>[Session started at 2010-02-20 13:41:49 -0800.] 2010-02-20 13:41:51.695 Untitledundotes[7373:20b] Insert Value 136 2010-02-20 13:41:51.715 Untitledundotes[7373:20b] FETCHED ENTITY 136 </code></pre> <p>As you can see, the object is present in the MOC after I try to undo its creation. Any suggestions as to what I am doing wrong?</p>
 

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