Something that has been on my mind for a long time is how similar objects are to programs, especially Unix programs. I'm not the first to notice this similarity, but the similarities are so numerous I find it striking. Here are a bunch of interesting things, in no particular order:

  • Executables are like classes. They both contain the code necessary to create new instances: for an executable, that would be a running program. For a class, that would be an instance.
  • Programs are best when they are small, focused, and do one thing well. Similarly, objects are best when they are small and focused. Is your class more like Microsoft Word, or cat?
  • Program reuse comes from this small focus. The same is true of objects.
  • Processes conceptually have a lifecycle. They're "garbage-collected" by the operating system when they finish executing, just like objects.
  • Processes are a combination of code and data, just like objects. Processes are independent of each other in a similar way to how instance data is independent between instances.
  • There are many ways processes can interact with one another, but the simplest seem very similar to the way objects should interact: via sockets. Socket communication is essentially the same as message passing between objects.
  • Long-lived objects seem awfully similar to server processes.

In the oo-vs-functional debate, I'm somewhere in the middle. I love functional programming – I just don't think it is somehow "more important" than object oriented programming, or that OO is misguided. Objects are just too general in concept and powerful in modeling ability. They even model functions rather well, and thus they can be used rather well for functional programming (when the syntax allows it; see Ruby).