Also, you're 100% right. The square brackets are what immediately repulsed me and continued to befuddle me even after years of experience with it. Also, everything just feels "backwards" to me if that makes any sense. Coming from Java/C#/JavaScript everything just seemed unintuitive to me at all times. Also, I think this was heavily compounded by using xCode which (at the time) was incredibly laggy. So, I'd mess up the Obj-C syntax and the IDE wouldn't tell me for what felt like forever. Often I'd make a change and hit "play" before the syntax highlighting caught up and that always felt infuriating.
I last used xCode about 4 years ago and it was still an issue then (even with swift).
Because it is. Obj-C comes from the Smalltalk lineage by way of Alan Kay, using message passing [0] versus method invocation. It's a subtle difference with huge implications to how you design systems. Method invocation won out mostly because of Java and C++, but there was a time it wasn't clear which was the better OO paradigm.
Quote from "How To Become a Hacker" by Eric S. Raymond: http://www.catb.org/esr/faqs/hacker-howto.html
https://cs.gmu.edu/~sean/stuff/java-objc.html
Even Java EE was actually a rebooted Objective-C based project done internally at Sun during the OpenSTEP days, aka Distributed Objects Everywhere.
"In contrast to the traditional technique of calling a program by name, message passing uses an object model to distinguish the general function from the specific implementations. The invoking program sends a message and relies on the object to select and execute the appropriate code."
Method invocation won out mostly because of Java and C++
but according to the wikipedia article java uses message passing.
supposedly the distinction is that i can have a generic method that gets called if a named method can not be found. in smalltalk that's doesNotUnderstand: in ruby it's method_missing. javascript used to have __noSuchMethod__, in php i can overload __call, in pike i do the same with defining a method called `(), and many more.
so are they all using message passing? and then if java is supposed to use message passing and javascript removed __noSuchMethod__ it seems that alone can't be the distinction.
if there is a distinction at all then it look more like an implementation detail that does not actually affect what kind of code you can write, and more importantly, based on that it is not at all clear that method invocation won out.
So, the gist of the difference is this: object-oriented programming is, at its core, about late binding. Specifically, delaying decisions about what code will run when until run-time. But there's still some wiggle room to decide how late certain decisions are made. Most mainstream object-oriented languages like Java and C# more-or-less wait until the start of run-time to decide, but at that point the mapping from argument type to which code is run is pretty much settled. (This isn't necessarily 100% true, but it's the general rule.)
In a system that uses message passing, it's pushed even later, to method invocation time. Basically, each object (actor, whatever) gets to decide what code will be executed to handle a message every time it receives a new message, even for messages of the same type. In practice, most the time it's always the same code. But the point is that this level of dynamicism is a first-class language feature and not just a thing you can accomplish with hacks.
Bona fide message passing is asynchronous. A message is sent and the send operation immediately returns, without blocking for a reply.
Nothing else should be called "message passing".
Also, you can change the destination of a message send at runtime, but you can't change the destination of a function call unless you're dtrace and can do code patching.
I've observed some folks have a visceral reaction to having to use Xcode, I don't really understand it myself. I can understand being annoyed at having to use a specific IDE to write iOS and Mac apps, e.g., it's harder to bring your own text editor like you usually can, it's going to make your life a lot harder if you try to to avoid using Xcode. But comparing Xcode to any IDEs like the JetBrains IDEs I've used (mainly the discontinued AppCode), Android Studio (also JetBrains under the hood), or other similarly complex development environments like Unreal or Unity, I don't see any of these as a clear winner. Personally I'd prefer using Xcode to any of those. I suspect this comes down to just whether you like native Mac apps or not, Xcode is a native Mac app and if you like that aesthetic than you'll like Xcode. I suspect most of the dislike for Xcode is really just folks who dislike the Mac platform (e.g., the UI toolkit) overall.
I feel like so much awesome engineering in XNU around security and portability, as well as innovations like IOKit are swept under the rug because "it's just FreeBSD."
I still think it's a shame that more people don't take advantage of the Mach side of XNU more. Launchd and Mach ports are a powerful combination IMO.
