Method Resolution

Method resolution is the step of determining which procedure to execute in response to a method invocation. For example, consider this scenario:

• Class "Dog" introduces a method "bark", and

• A subclass of "Dog", called "BigDog", overrides "bark", and

• A client program creates an instance of either "Dog" or "BigDog" (depending on some run-time criteria) and invokes method "bark" on that instance.

Method resolution is the process of determining, at run time, which method procedure to execute in response to the method invocation (either the method procedure for "bark" defined by "Dog", or the method procedure for "bark" defined by "BigDog"). This determination depends on whether the receiver of the method (the object on which it is invoked) is an instance of "Dog" or "BigDog" (or perhaps depending on some other criteria).

SOM allows class implementors and client programs considerable flexibility in deciding how SOM performs method resolution. In particular, SOM supports three mechanisms for method resolution, described in order of increased flexibility and increased computational cost: offset resolution, name-lookup resolution, and dispatch-function resolution.