Alan Kay: Smalltalk is not about objects, it’s about messaging (1998)

I think the key insight of Smalltalk can be grasped just by thinking about how Smalltalk does branching. A line from the GNU Smalltalk tutorial: mybool ifTrue: [ ^ 2 / 4 roundup ] The outer part of this expression reads “send a closure expression, as the message ifTrue, to the receiver mybool.” Keep in mind, this `mybool` could be anything! It just so happens that there are two runtime objects, `true` and `false`, that satisfy the “Boolean interface” (consisting…

I find it interesting that everyone gets so up-beat about the ideology or philosophical debate about objects sending each object messages, hell even not relying to a message one object send you until a later date. Without even thinking about concurrency, state, and hell even the basics such as cyclic loops within a event based system! Though I keep hearing from Alan and other prominent language designers that we still are holding onto this old 1960 mental model of command…

Yes! This is something it took me a long time to internalize but is something I absolutely love about Objective-C. Regardless of any technical differences between message passing and method calling, there was a real shift in how I thought about the process. When I started thinking about object interaction as message passing, it made me write better encapsulated code. I'm not sure exactly what it is, I think that part of it is that to me a “message” sounds…