The Objective-C Runtime and Swift Dynamism (opens in new tab)

> What is cross-platform development like?

Sorry, never tried that.

> Also, what about Objective-C prevents business logic bugs?

Generically speaking C makes it easy to interact with the computer memory but harder to abstract things while OO languages have it reverse.

C has GOTO, Objective-C not.

Objective-C has objects that easily can encapsulate different aspects of your logic. Objective-C is very verbose and readable while most C API's aren't.

Obviously Swift is even better in that regard as it has better types and checks but it doesn't allow you to seamlessly use C.

When arguing against a “common misconception,” one typically provides a source.

You seem to be saying that Apple’s claims are not only wrong, but ObjC is somehow faster despite having to do more work. Swift has no runtime method table lookups, no extra objc_msgSend calls, better ability to analyze and inline code, no retain/release dance for code with value semantics, etc. Every benchmark I’ve seen shows Swift faster for these reasons.

I can't speak for other people's code, but I regularly profile and read the machine code generated by the Swift compiler, at least for my hot loops. If you know what you are doing (use the right annotations and optimizer flags), even fairly generic code often compiles down to something that comes very close to what an optimizing C compiler would generate. Sometimes it generates even faster code, because the Swift calling convention can make better use of available registers. Sure, there are situations where it generates less optimal code, but generally generic idiomatic Swift is on a different level than a (non-profiling) compiler for idiomatic Objective-C can ever come close to. That's my experience.

Is that lookup done all the time (for each invocation of the same method):? Or is it done at a single point in time, like a JIT, but after that the method is “fixed”?

With the possibility to intercept/replace code at runtime (at any time, not just at a resolve/jit stage) it must be very hard for the runtime to optimize calls (i.e make direct calls instead of indirect via method pointer lookup)?

I’m not familiar with how this works in any runtime (V8, Hotspot, ...) so I’m curious which runtimes actually pay one extra method pointer lookup forever and which don’t. I’m guessing the answer for nearly all of them is “it depends”.

So more or less dynamic dispatch then?

It's interesting that Swift is a static language, despite having the lightweight modern syntax similar to Python or Ruby. Though I suppose Go is the same way.