KVCcompatible

KVC-compatible refers to objects that can participate in Key-Value Coding (KVC), a mechanism in Cocoa and Cocoa Touch that allows properties to be accessed and modified using string keys rather than direct method calls. KVC is commonly used by frameworks such as Cocoa bindings, Core Data, and scripting bridges, enabling dynamic interaction with an object's data.

KVC works by routing requests such as valueForKey: and setValue:forKey: to the appropriate property or accessor. If an object has a property named "name," a KVC-compliant implementation provides accessors named name and setName:. If the key does not correspond to a real property, the object can override valueForUndefinedKey: or setValue:forUndefinedKey: to supply custom behavior. KVC also supports valueForKeyPath: to traverse nested objects. While many Objective-C properties are KVC-compliant by default, nonstandard accessors or dynamic storage require explicit support.

Implementing KVC compatibility typically involves exposing standard accessors, or overriding the key-value methods to customize behavior. In Objective-C, declaring a property or providing corresponding getter and setter methods suffices. In cases of dynamic data, an object may provide valueForKey: and setValue:forKey: implementations, or override valueForUndefinedKey:. Swift can participate in KVC for classes that inherit from NSObject and expose @objc or dynamic members, using value(forKey:) and setValue(_:forKey:) through the bridging layer.

KVC-compatibility is often a prerequisite for features like data bindings and Core Data fetches, where the runtime relies on string keys to access model properties. It remains distinct from type safety, focusing on dynamic, key-based access to an object’s data.