Setmetatablet

Setmetatablet is a programming construct used in certain languages to attach a metatable to an object, enabling customized behavior for operations and property access. It is conceptually similar to Lua's setmetatable function but is not a standard feature of Lua or other mainstream languages. In practice, setmetatablet appears in educational languages, niche libraries, and some framework code to illustrate prototype-like inheritance and behavioral delegation.

The typical usage involves calling setmetatablet with two arguments: a target object and a metatable that defines metamethods. The metatable is a map or table of special keys such as __index, __newindex, __call, and __tostring, each associated with a function or value that specifies the object's behavior when that operation occurs.

Semantics: Depending on the language, setmetatablet may mutate the target object in place or return a new object with the metatable applied. The resulting object will use the metamethods for operations that would otherwise be default.

Common usage patterns include implementing simple inheritance via __index lookup to a prototype, providing controlled access by using __newindex to validate writes, and enabling object-to-string customization with __tostring.

Limitations: Metatables can make code harder to reason about and optimize, may introduce performance overhead, and some environments restrict metamethod definitions for security or portability.

See also setmetatable, metatable, metamethod.