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

Comment on Alan Kay on the Meaning of “Object-Oriented Programming” (2003)parent

I think it's a bit charitable to call what Objective C does to be "message passing". The messages are not asynchronous and have only a single recipient, so in practice I would say they're method calls with late binding.

mpweiher 11y

However, they can easily be made asynchronous and address multiple recipients. See Higher Order Messaging[1][2], first implemented in Objective-C[3]. So for example:

    [[myView onMainThread] setNeedsDisplay:YES];

    result = [[someObject future] someMessage:arg];

    combined = [[prefixes collect] stringByAppendingString:[suffixes each]];

The reason this is easy in Objective-C is because its brand of message passing is just (barely) powerful enough to qualify as message passing. In fact, if you squint just a little, you can see it as fully reified message passing with the common-case (a synchronous method is invoked) optimized.

[1] http://en.wikipedia.org/wiki/Higher_order_message

[2] http://www.metaobject.com/papers/Higher_Order_Messaging_OOPS...

[3] https://github.com/mpw/MPWFoundation

xsmasher 11y

At least you can redirect messages to another recipient, and write a handler for "unhandled messages." Impossible with c++, at least with standard method calls.

archagon 11y

You can do one-to-many messages via notifications, though it's less elegant.

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