CSC/ECE 517 Fall 2010/ch5 5c IC
Dynamic Dispatch
Introduction
Dynamic dispatch is an object-oriented programming concept that refers to the mapping of a method to an object's dynamic runtime type. It is common in many object-oriented languages. Languages such as Java and C++ use single dispatch, while only a few, such as CLOS, use multiple dispatch. Both types of dispatch will be discussed later.
Advantages
- Flexibility
- Extensibility
Disadvantages
- Lookup overhead
- Counter to safety and increased compile-time knowledge
- Obstacle to optimization
- Hinders compiler in determining exact type of objects
Example in C++
class A
{
int aMember1;
public:
virtual int method1();
virtual void method2();
};
class B : public A
{
int bMember1;
public:
virtual int method1();
virtual double method3();
}
Single vs Multiple Dispatch
Dynamic dispatch comes in 2 types: single and multiple dispatch.
References
[1] “Dynamic Dispatch in Object-Oriented Languages”, 2004.
[2] M. Muller, “Message Dispatch in Dynamically-Typed Object-Oriented Languages”, Master’s Thesis, University of New Mexico, 1995.