methodSignatureForSelector

A method signature is a formal specification that identifies a method by its essential elements, typically including the method name and the number and types of its parameters. It functions as the unique identifier used by a compiler or runtime to resolve which method to invoke when a call is made. The signature is distinct from the method body and, in many languages, from the return type.

In most languages, the signature comprises the method name and the ordered list of parameter types (and sometimes the number of parameters). Parameter names are generally not part of the signature, and the return type is often not included in the signature for overload resolution. Some languages also include generic type parameters as part of the signature, or treat variadic and default parameters differently, which can affect overload selection.

Language-specific rules vary. For example, Java uses the method name plus parameter types to form the signature, with the return type excluded from the signature; overload resolution is based on these types. In C# and C++, the signature similarly focuses on name and parameter list, while return types do not enable overloading by themselves. Python uses the function’s parameter list as its signature, with type hints optional. Kotlin and Swift incorporate parameter labels and default values in certain overload contexts.

Understanding signatures is important for API design, reflection, and debugging. Changing a signature is typically a breaking change, affecting compatibility, overload resolution, and call sites.