CoreData使用须知

1.首先需要创建core data 的上下文环境NSManagedObjectContext；

2.NSManagedObjectContext 需要 setPersistentStoreCoordinator：（NSPersistentStoreCoordinator*）

3.NSPersistentStoreCoordinator，需要包含数据存储的位置，以及数据中包含的NSManagedObjectModel；如文档中描述Instances ofNSPersistentStoreCoordinator associate persistent stores (by type) with a model (or more accurately, a configuration of a model) and serve to mediate between the persistent store or stores and the managed object context or contexts.