我是Obj-C和CoreData的新手。我过去成功使用过CoreData，但是当我尝试为我的一个托管对象中的属性赋值时，我遇到了问题。
所以，我所在的地方是我已经实例化了我的managedObjectContext并创建了一个托管对象来保存。
if (managedObjectContext == nil)
{
managedObjectContext = [(AppDelegate *)[[UIApplication sharedApplication] delegate] managedObjectContext];
}
Lesson *Lesson1 = [NSEntityDescription insertNewObjectForEntityForName:@"Lesson" inManagedObjectContext:managedObjectContext];
然后我去编辑managedObject的值并将其保存：
Lesson1.productID = 1;
Lesson1.purchaseStatus = 1;
Lesson1.title = @"Happy Birthday to You";
Lesson1.subtitle = @"Patty & Mildred Hill";
Lesson1.titleAndSubtitle = @"Happy Birthday to You - Patty & Mildred Hill";
Lesson1.coverArtFilename = @"beethoven.png";
Lesson1.durationLabel = @"0:11";
Lesson1.notes = @"123";
Lesson1.timing = @"3/4";
Lesson1.keySignature = @"G";
Lesson1.difficultyImageFilename = @"easy.png";
Lesson1.lessonDescription = @"Originally, this song piece was called 'Good Morning to All' and was sung to and by children in school.";
Lesson1.sheetFilename = @"1_score";
Lesson1.midiFilename = @"happyBirthdayToYou";
Lesson1.materialsFilename = @"1_score";
Lesson1.roll = @"happyBirthdayToYou";
Lesson1.duration = 11;
Lesson1.startingIndicatorPosition = 175;
Lesson1.rollPositionArray = [NSArray arrayWithObjects: /* 0 */ [NSNumber numberWithInteger:0],
/* 1 */ [NSNumber numberWithInteger:0],
/* 2 */ [NSNumber numberWithInteger:0],
/* 3 */ [NSNumber numberWithInteger:-65],
/* 4 */ [NSNumber numberWithInteger:-100],
/* 5 */ [NSNumber numberWithInteger:-135],
/* 6 */ [NSNumber numberWithInteger:-185],
/* 7 */ [NSNumber numberWithInteger:-185],
/* 8 */ [NSNumber numberWithInteger:-241],
/* 9 */ [NSNumber numberWithInteger:-306],
/* 10 */ [NSNumber numberWithInteger:-341],
/* 11 */ [NSNumber numberWithInteger:-376],
/* 12 */ [NSNumber numberWithInteger:-426],
/* 13 */ [NSNumber numberWithInteger:-426],
/* 14 */ [NSNumber numberWithInteger:-483],
/* 15 */ [NSNumber numberWithInteger:-548],
/* 16 */ [NSNumber numberWithInteger:-582],
/* 17 */ [NSNumber numberWithInteger:-617],
/* 18 */ [NSNumber numberWithInteger:-666],
/* 19 */ [NSNumber numberWithInteger:-701],
/* 20 */ [NSNumber numberWithInteger:-737],
/* 21 */ [NSNumber numberWithInteger:-799],
/* 22 */ [NSNumber numberWithInteger:-834],
/* 23 */ [NSNumber numberWithInteger:-868],
/* 24 */ [NSNumber numberWithInteger:-918],
nil];
NSError *error;
if (![managedObjectContext save:&error]) {
NSLog(@"Whoops, couldn't save: %@", [error localizedDescription]);
}
此时，如果我运行应用程序，它会在尝试更改productID的值时给出错误：EXC_BAD_ACCESS（code = 2，address = 0x1）。它还给了我一个警告，声明它是一个“不兼容的整数指针转换，从”int“分配给”int *“。
我做了一些调试并检查我的对象是否为零，而不是。当我输出我的managedObjectContext的描述时，我得到：
Printing description of self->managedObjectContext:
<NSManagedObjectContext: 0x7e8d8b0>
打印我的物品，我得到：
Printing description of Lesson1:
<NSManagedObject: 0x7e927e0> (entity: Lesson; id: 0x7e7fce0 <x-coredata:///Lesson/tA7BFE664-F978-4983-B5DC-14D3F3ED49812> ; data: {
coverArtFilename = nil;
difficultyImageFilename = nil;
duration = 0;
durationLabel = nil;
keySignature = nil;
lessonDescription = nil;
materialsFilename = nil;
midiFilename = nil;
productID = nil;
purchaseStatus = 0;
roll = nil;
rollPositionArray = nil;
sheetFilename = nil;
startingIndicatorPosition = 0;
subtitle = nil;
timing = nil;
title = nil;
titleAndSubtitle = nil;
})
由于我的知识很少，我的调试技巧有限，所以如果有人能指出我正确的方向，我会非常感激。谢谢。
修改
我的NSManagedObjectContext是以默认方式定义的。我在下面附上了我的AppDelegate.m：
#import "AppDelegate.h"
@implementation AppDelegate
@synthesize window = _window;
@synthesize managedObjectContext = __managedObjectContext;
@synthesize managedObjectModel = __managedObjectModel;
@synthesize persistentStoreCoordinator = __persistentStoreCoordinator;
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
return YES;
}
- (void)applicationWillResignActive:(UIApplication *)application
{
// Sent when the application is about to move from active to inactive state. This can occur for certain types of temporary interruptions (such as an incoming phone call or SMS message) or when the user quits the application and it begins the transition to the background state.
// Use this method to pause ongoing tasks, disable timers, and throttle down OpenGL ES frame rates. Games should use this method to pause the game.
}
- (void)applicationDidEnterBackground:(UIApplication *)application
{
// Use this method to release shared resources, save user data, invalidate timers, and store enough application state information to restore your application to its current state in case it is terminated later.
// If your application supports background execution, this method is called instead of applicationWillTerminate: when the user quits.
}
- (void)applicationWillEnterForeground:(UIApplication *)application
{
// Called as part of the transition from the background to the inactive state; here you can undo many of the changes made on entering the background.
}
- (void)applicationDidBecomeActive:(UIApplication *)application
{
// Restart any tasks that were paused (or not yet started) while the application was inactive. If the application was previously in the background, optionally refresh the user interface.
}
- (void)applicationWillTerminate:(UIApplication *)application
{
// Saves changes in the application's managed object context before the application terminates.
[self saveContext];
}
- (void)saveContext
{
NSError *error = nil;
NSManagedObjectContext *managedObjectContext = self.managedObjectContext;
if (managedObjectContext != nil) {
if ([managedObjectContext hasChanges] && ![managedObjectContext save:&error]) {
// Replace this implementation with code to handle the error appropriately.
// abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
abort();
}
}
}
#pragma mark - Core Data stack
// Returns the managed object context for the application.
// If the context doesn't already exist, it is created and bound to the persistent store coordinator for the application.
- (NSManagedObjectContext *)managedObjectContext
{
if (__managedObjectContext != nil) {
return __managedObjectContext;
}
NSPersistentStoreCoordinator *coordinator = [self persistentStoreCoordinator];
if (coordinator != nil) {
__managedObjectContext = [[NSManagedObjectContext alloc] init];
[__managedObjectContext setPersistentStoreCoordinator:coordinator];
}
return __managedObjectContext;
}
// Returns the managed object model for the application.
// If the model doesn't already exist, it is created from the application's model.
- (NSManagedObjectModel *)managedObjectModel
{
if (__managedObjectModel != nil) {
return __managedObjectModel;
}
NSURL *modelURL = [[NSBundle mainBundle] URLForResource:@"iLessons_Piano" withExtension:@"momd"];
__managedObjectModel = [[NSManagedObjectModel alloc] initWithContentsOfURL:modelURL];
return __managedObjectModel;
}
// Returns the persistent store coordinator for the application.
// If the coordinator doesn't already exist, it is created and the application's store added to it.
- (NSPersistentStoreCoordinator *)persistentStoreCoordinator
{
if (__persistentStoreCoordinator != nil) {
return __persistentStoreCoordinator;
}
NSURL *storeURL = [[self applicationDocumentsDirectory] URLByAppendingPathComponent:@"iLessons_Piano.sqlite"];
NSError *error = nil;
__persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[self managedObjectModel]];
if (![__persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeURL options:nil error:&error]) {
/*
Replace this implementation with code to handle the error appropriately.
abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
Typical reasons for an error here include:
* The persistent store is not accessible;
* The schema for the persistent store is incompatible with current managed object model.
Check the error message to determine what the actual problem was.
If the persistent store is not accessible, there is typically something wrong with the file path. Often, a file URL is pointing into the application's resources directory instead of a writeable directory.
If you encounter schema incompatibility errors during development, you can reduce their frequency by:
* Simply deleting the existing store:
[[NSFileManager defaultManager] removeItemAtURL:storeURL error:nil]
* Performing automatic lightweight migration by passing the following dictionary as the options parameter:
[NSDictionary dictionaryWithObjectsAndKeys:[NSNumber numberWithBool:YES], NSMigratePersistentStoresAutomaticallyOption, [NSNumber numberWithBool:YES], NSInferMappingModelAutomaticallyOption, nil];
Lightweight migration will only work for a limited set of schema changes; consult "Core Data Model Versioning and Data Migration Programming Guide" for details.
*/
NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
abort();
}
return __persistentStoreCoordinator;
}
#pragma mark - Application's Documents directory
// Returns the URL to the application's Documents directory.
- (NSURL *)applicationDocumentsDirectory
{
return [[[NSFileManager defaultManager] URLsForDirectory:NSDocumentDirectory inDomains:NSUserDomainMask] lastObject];
}
@end
答案 0 :(得分：4)
不是productID或任何其他数字属性NSNumber*？你能试试吗
Lesson1.productID = [NSNumber numberWithInt:1];
purchaseStatus，duration和startingIndicatorPosition