methodmissing

Method_missing is a mechanism for handling calls to methods that are not defined on an object. It is most closely associated with Ruby, where it enables dynamic behavior, delegation, and domain-specific languages by intercepting undefined method messages.

In Ruby, method_missing is defined on Object. When a call arrives for a method that cannot be resolved, Ruby invokes method_missing(name, *args, &block). Inside, a program can inspect the requested name and arguments, forward the call to another object, synthesize a value, or delegate to a different path. If the handler cannot process the request, it should call super to raise NoMethodError as usual.

Common patterns include dynamic finders or attribute access on a hash-like object. For example, a method_missing can route names starting with get_ to a data store lookup. Implementations often pair method_missing with respond_to? (and, in modern Ruby, respond_to_missing? to reflect the dynamic capabilities) so that introspection continues to be meaningful.

Considerations include performance impact, increased code complexity, and potential security issues if method resolution accepts arbitrary input. It is recommended to use method_missing sparingly, document behavior clearly, and define respond_to? consistently so code that relies on introspection continues to function.

Outside Ruby, similar concepts exist under different names. Python uses __getattr__ and __getattribute__; JavaScript offers Proxy-based interception; other languages provide dynamic dispatch hooks or reflection-based delegation. method_missing remains a powerful but potentially risky tool for advanced metaprogramming and DSL construction.