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This may seem stupid, but I still couldn't figure out how to mark a attribute as a primary key in the xcdatamodel file. My persistent storage is sqlite file. Can anyone help me?
In that case, how can I "validate" a ID to be unique? Should I write a validation method or something?
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The answer is NO. To achieve similar thing, You can have an 'id' field in the table, before inserting into the table get the maximum value of the 'id' and then add 1 to the value. With a filed 'userID' in the table ENTITY_USER (users), the get the highest user ID.
Core Data is an object graph and persistence framework provided by Apple in the macOS and iOS operating systems. It was introduced in Mac OS X 10.4 Tiger and iOS with iPhone SDK 3.0. It allows data organized by the relational entity–attribute model to be serialized into XML, binary, or SQLite stores.
Core Data is not a database. Core Data is a framework for managing an object graph. An object graph is nothing more than a collection of interconnected objects. The framework excels at managing complex object graphs.
There are two steps to storing an array of a custom struct or class in Core Data. The first step is to create a Core Data entity for your custom struct or class. The second step is to add a to-many relationship in the Core Data entity where you want to store the array.
Your options are:
-[NSManagedObject objectID]. Note that this ID is temporary until either the object is saved for the first time or you call -[NSManagedObjectContext obtainPermanentIDsForObjects:error:] CFUUID family of functions to generate a UUID for each object in your -awakeFromInsert methodThere is no good way to validate that a property is unique. The closest you'll get is to ensure it is unique at creation time, and then implement a custom setter method that stops anyone ever changing the ID.
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