Question

我正在将核心数据集成到我的应用程序中，我已经有了一个sqllite数据库文件。我应该创建一个新的，以使其更容易，或者我应该使用现有的。对于很多问题我很抱歉，谢谢你提前!!

另外，我该如何创建一个新的？

我将以下方法实现到appdelegate（没有错误），但是我不知道在文本字段中放什么

这是什么？ “myCoreData”是用.xcdatamodeld结尾创建的核心数据db的名称吗？如果是这样，妈妈是什么？

NSURL *modelURL = [[NSBundle mainBundle] URLForResource:@"myCoreData" withExtension:@"momd"];

这是什么？这是创建数据库，还是我应该创建它并将信息放在这里？这存储在哪里？

NSURL *storeURL = [[self applicationDocumentsDirectoryModified] URLByAppendingPathComponent:@"coreDataDB.sqlite"];

这是实施

- (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 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:@"myCoreData" 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 applicationDocumentsDirectoryModified] URLByAppendingPathComponent:@"coreDataDB.sqlite"];

    NSError *error = nil;
    _persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[self managedObjectModel]];
    if (![_persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeURL options:nil error:&error]) {

        NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
        abort();
    }

    return _persistentStoreCoordinator;
}

Answer 1

没有使用魔法记录，结束了从xcode中的新项目添加样板代码。启动一个simgle视图应用程序，单击coredata，转到adddelegate，底部是你需要的大多数方法。

为了方便起见，我用coredata所需的所有方法创建了一个传播者。

将核心数据实现到现有应用程序中，创建或不写入sqlite

1 个答案: