问题
What does this part of Apple core data documentation means?
User Info Dictionaries
Many of the elements in a managed object model—entities, attributes, and relationships—have an associated user info dictionary. You can put whatever information you want into a user info dictionary, as key-value pairs. Common information to put into the user info dictionary includes version details for an entity, and values used by the predicate for a fetched property.
I understand that by default entities have that dictionary, but I'm not able to find find userInfo on coredata entities or attributes.
回答1:
Get the NSEntityDescription from your NSManagedObject (through the entity property) or from your NSManagedObjectModel and get the NSAttributeDescription through attributesByName. This gives you a dictionary where you get the proper Description by name which has the userInfo as a property as well.
NSManagedObject *managedObject;
NSEntityDescription *entityDescription = managedObject.entity;
NSAttributeDescription *attributeDescription = entityDescription.attributesByName[@"someAttribute"];
NSString *foo = attributeDescription.userInfo[@"foo"];
来源：https://stackoverflow.com/questions/17230614/userinfo-dictionaries-on-coredata