On: Alan Kay on the Meaning of “Object-Oriented Programming” (2003)

[chrisseaton]

> However I don't think anything in the Ruby docs ever claims that it has a message-passing intent.

There is of course the `Kernel#send` method, which implies the model is messages being sent. It's not called `call`.

[inopinatus → chrisseaton]

I think you mean Object#send? I actually think that's misnamed, I think it should be named Object#receive because that's what happens - you're forcing an object to receive a symbol for (by default) dispatch through its method table.

The fact it isn't invoked for regular method invocation is kinda indicative of Ruby _not_ being a pure message passing language, even if we like treating it that way.

[chrisseaton → inopinatus]

> I think you mean Object#send?

It's definitely Kernel#send. Object defines no instance methods at all.

    > Kernel.instance_methods(false).include?(:send)
    => true
    > Object.instance_methods(false).include?(:send)
    => false
    > Object.instance_methods(false)
    => []

https://github.com/ruby/ruby/blob/v2_6_2/vm_eval.c#L2163

[inopinatus → chrisseaton]

Fascinating, the docs are misleading on this point. http://ruby-doc.org/core-2.6.2/Object.html#method-i-send because Object includes Kernel and it's just easier to find, I guess.

That's a somewhat arcane implementation detail though. What about the meat of the discussion?

[chrisseaton → inopinatus]

I don't think Ruby is message passing either because the caller determines which method to call, based on the object's method table. #method_missing is just another method to be called by the caller - it isn't an example of the object being able to determine what happens. I think #send is really #call, but I think the name implies someone somewhere thought it was message passing.

If I'm being uncharitable I think applying the term 'message passing' to Ruby is a bit of making something sound more sophisticated and elaborate than it is. They're method calls - it's pretty simple already and doesn't need a complex concept on top of that.

[inopinatus → chrisseaton]

It merely remains to fork and/or invent a language that otherwise looks almost exactly like Ruby but with message passing only.

[macintux → inopinatus]

Elixir?

[chrisseaton → macintux]

Elixir has conventional method calls by default, and only optional message passing with a separate syntax. It's definitely not message passing everywhere.

[macintux → chrisseaton]

It’s message passing everywhere outside the current object (process).

It’s a little tough to compare to an OO language because there are no classes, but all object to object communications are asynchronous messages.