andsetValueforKeyPath

andsetValueforKeyPath is not a distinct API, but a term that commonly refers to the Cocoa Key-Value Coding (KVC) method setValue:forKeyPath:. This method enables setting a value on an object that is reached by a dot-delimited key path, such as "address.city" or "config.defaultSettings.enabled". It is available on NSObject and is a core part of KVC in the Foundation framework.

How it works: At runtime, setValue:forKeyPath: traverses the object graph following each key component in the path. The final component identifies the property to assign the provided value to. Each intermediate object along the path must exist and be KVC-compliant for reading and writing. If a key is unknown, or an intermediate object is nil, a runtime exception may be raised.

Usage example (Objective-C): [person setValue:@\"New York\" forKeyPath:@\"address.city\"]; Example in Swift (via bridging) is similar, using the same method on an Objective-C accessible object. The value provided must be compatible with the final property's type, and the target must be KVC-compliant for assignment.

Considerations: setValue:forKeyPath: is powerful for dynamic property access, data binding, and UI code that reacts to model changes. It relies on the key-value coding compliance of properties (usually via KVC-compliant accessors or ivars). It is not suitable for every situation and can lead to runtime exceptions if paths are invalid or intermediate objects are nil. The feature is often discussed alongside valueForKeyPath: and setValue:forKey:, which handle reading and direct writes, respectively.