把你之前创建的实体文件全部删除掉,把沙盒中的数据库文件删除掉,实体只保持一个,然后重新创建出实体文件.
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
NSLog(@"%@", NSHomeDirectory());
// 创建两条记录
[self createStudent:@"YouXianMing" age:[NSNumber numberWithInt:26]];
[self createStudent:@"QiuLiang" age:[NSNumber numberWithInt:27]];
// 存储记录
[self saveContext];
// 设定要查询的实体
NSFetchRequest *fetch = [NSFetchRequest fetchRequestWithEntityName:@"Student"];
// 取出查询结果
NSArray *students = [[self managedObjectContext] executeFetchRequest:fetch error:nil];
[students enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
Student *student = obj;
NSLog(@"%@ %@", student.age, student.name);
}];
return YES;
}
- (Student *)createStudent:(NSString *)name age:(NSNumber *)age
{
// 实体描述信息
NSEntityDescription *description = [NSEntityDescription entityForName:@"Student"
inManagedObjectContext:[self managedObjectContext]];
// 初始化对象
Student *student = [[Student alloc] initWithEntity:description
insertIntoManagedObjectContext:[self managedObjectContext]];
student.name = name;
student.age = age;
return student;
}
然后我们给这个Student表新增加一个属性然后进行数据库的版本升级.
首先,我们先创建新的数据库表版本.
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
NSLog(@"%@", NSHomeDirectory());
// 存储记录
[self saveContext];
// 设定要查询的实体
NSFetchRequest *fetch = [NSFetchRequest fetchRequestWithEntityName:@"Student"];
// 取出查询结果
NSArray *students = [[self managedObjectContext] executeFetchRequest:fetch error:nil];
[students enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
Student *student = obj;
NSLog(@"%@ %@ %@", student.age, student.name, student.sex);
}];
return YES;
}
运行后会崩溃,提示不兼容.
找到以下地方.
将nil替换成如下的形式.
然后运行.
http://stackoverflow.com/questions/8881453/the-model-used-to-open-the-store-is-incompatible-with-the-one-used-to-create-the
Deleting the app is sometimes not the case! Suggest, your app has already been published! You can‘t just add new entity to the data base and go ahead - you need to perform migration!
For those who doesn‘t want to dig into documentation and is searching for a quick fix:
- Open your .xcdatamodeld file
- click on Editor
- select Add model version...
- Add a new version of your model (the new group of datamodels added)
- select the main file, open file inspector (right-hand panel)
- and under
Versioned core data model select your new version of data model for current data model
- THAT‘S NOT ALL ) You should perform so called "light migration".
- Go to your
AppDelegate and find where the persistentStoreCoordinator is being created
- Find this line
if (![_persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeURL options:nil error:&error])
- Replace
nil options with @{NSMigratePersistentStoresAutomaticallyOption:@YES, NSInferMappingModelAutomaticallyOption:@YES} (actually provided in the commented code in that method)
- Here you go, have fun!
P.S. This only applies for lightweight migration. For your migration to qualify as a lightweight migration, your changes must be confined to this narrow band:
- Add or remove a property (attribute or relationship).
- Make a nonoptional property optional.
- Make an optional attribute nonoptional, as long as you provide a default value.
- Add or remove an entity.
- Rename a property.
- Rename an entity.
