Core Data

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. The data can be manipulated using higher level objects representing entities and their relationships. Core Data manages the serialized version, providing object lifecycle and object graph management, including persistence. Core Data interfaces directly with SQLite, insulating the developer from the underlying SQL. Just as Cocoa Bindings handle many of the duties of the controller in a model–view–controller design, Core Data handles many of the duties of the data model. Among other tasks, it handles change management, serializing to disk, memory footprint minimization and queries against the data.

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. The data can be manipulated using higher level objects representing entities and their relationships. Core Data manages the serialized version, providing object lifecycle and object graph management, including persistence. Core Data interfaces directly with SQLite, insulating the developer from the underlying SQL. Just as Cocoa Bindings handle many of the duties of the controller in a model–view–controller design, Core Data handles many of the duties of the data model. Among other tasks, it handles change management, serializing to disk, memory footprint minimization and queries against the data. ==Usage== Core Data describes data with a high level data model expressed in terms of entities and their relationships plus fetch requests that retrieve entities meeting specific criteria. Code can retrieve and manipulate this data on a purely object level without having to worry about the details of storage and retrieval. The controller objects available in Interface Builder can retrieve and manipulate these entities directly. When combined with Cocoa bindings the UI can display many components of the data model without needing background code. For example: a developer might be writing a program to handle vCards. In order to manage these, the author intends to read the vCards into objects, and then store them in a single larger XML file. Using Core Data the developer would drag their schema from the data designer in Xcode into an interface builder window to create a GUI for their schema. They could then write standard Objective-C or Swift code to read vCard files and put the data into Core Data managed entities. From that point on the author's code manipulates these Core Data objects, rather than the underlying vCards. Connecting the Save menu item to the appropriate method in the controller object will direct the controller to examine the object stack, determine which objects are dirty, and then re-write a Core Data document file with these changes. Core Data is organized into a large hierarchy of classes, though interaction is only prevalent with a small set of them. Sources:

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