Dispatch table


In computer science, a dispatch table is a table of pointers or memory addresses to functions or methods. Use of such a table is a common technique when implementing late binding in object-oriented programming.
It is primarily used to simplify program lines and reduce lines of code.

In different programming languages

Perl

The following shows one way to implement a dispatch table in Perl, using a hash to store references to code.

  1. Define the table using one anonymous code-ref and one named code-ref
my %dispatch = ;
sub say_goodbye
  1. Fetch the code ref from the table, and invoke it
my $sub = $dispatch;
print $sub ? $sub-> : "unknown argument\n";

Running this Perl program as perl greet -h will produce "hello", and running it as perl greet -g will produce "goodbye".

JavaScript

Following is a demo of implementing a dispatch table in JavaScript:
const thingsWeCanDo = ;
function doSomething

Lua

In Lua, this behavior is supported and encouraged. Here is an example:
local colors =
print
local choice = io.read
local color = colors
if color then
print
end

Virtual method tables

In object-oriented programming languages that support virtual methods, the compiler will automatically create a dispatch table for each object of a class containing virtual methods. This table is called a virtual method table or vtable, and every call to a virtual method is dispatched through the vtable.