KeyPathRoot

KeyPathRoot is a term used to describe the starting object in a key-path expression. It serves as the anchor from which a sequence of property or relationship accesses is evaluated within an object graph. In a path such as address.street, the KeyPathRoot would be the root object that contains the address property.

In practice, KeyPathRoot appears in various programming contexts. In languages with key-path syntax, such as Swift or Objective-C with key-value coding, the root is the object on which the path is applied to obtain a value. In data-binding and ORM frameworks, the root object provides the initial context for resolving subsequent path segments, which may traverse nested objects, collections, or optional relationships.

Semantics and behavior are influenced by the framework’s rules. A path path segments are resolved in sequence, and if any intermediate segment yields nil or an invalid result, the overall value may become nil or trigger a fallback. The root itself is not part of the path string, but it determines the type and scope of the entire key-path expression. Changes to the root alter the outcome of the path evaluation, and some systems support re-binding to a different root without modifying the path.

KeyPathRoot is commonly used in data-binding, serialization, and query translation, where a consistent starting point enables uniform traversal of complex object graphs. While the precise terminology varies, the concept remains the same: a defined context object from which a key-path expression begins.

See also: KeyPath, Key-Value Coding, Path, Data binding.