ROR made Ruby into a mainstream language from a single success story and a usable tool. Swift already has a much bigger developer base, there's no reason it couldn't succeed in other markets as well given the right catalyst.
I don't follow your argument. Ruby is a single-use-case language so therefore Swift must also be? I can point to many languages which have achieved adoption in more than one domain as counter-examples.
That is just libobjc, which is basically useless except if you actually plan to reimplement everything Foundation does. ObjC IS de-facto Foundation, without NSString, NSArray, etc no library will ever work. GNUStep is more likely to be considered a decent multi-platform implementation of an Objective-C runtime, or WinObjC from Microsoft.
Apple has a bigger developer base but they are captive users. I'm not saying swift isn't good, but nobody actually chooses to use it. They use because it is the language for making iDevice apps.
The problem is that if people are only using a language because they have to, then they are not as incentivised to create the open source projects that swift needs. Ruby had a large number of very enthusiastic users, that's what made the difference.
I think you're describing a chicken-and-egg problem, and you're overstating the extent to which a gap exists in terms of library support.
Swift has a very capable standard library, a high-quality, officially supported networking library, and fantastic C and Python interop which can fill a lot of the gaps to the extent they exist.
Even in its current state, I can imagine Swift being productive in something like server-less development, where it would offer a nice strongly typed alternative to scripting languages which currently dominate the space.
Swift has a lot of intrinsic features which would make it nice to use for server-side development, and I'm sure it would find plenty of users if there were a strong success story to point to.
Given the number of users, I'm not convinced the absolute number of Ruby users in 2009 was larger than the number of "swift enthusiasts" today.
Have you used the Python interop? I went looking to try it a few months ago and it was MIA as far as I could tell. It seems to be exclusively baked into Tensorflow's fork of the compiler. I would love a pointer if I missed something!
The captive bit isn't entirely true, as the language has had Objective-C for competition.
I suspect that instead of an enthusiasm gap the greater negative impact on FOSS libraries comes from the Apple-platform dev community being strongly oriented around making consumer-focused programs for money.
Objective-C is neither easy nor something most people liked. I did actually like it because I always thought it was really cool, but most people I talked with hate it with a passion. For the average Java developer, choosing between Swift and Objective-C is like choosing between cake and a tomato for dessert. Some people might pick Objective-C, but it's definitely not the majority.
Funny, when Mac OS X was released, it had two programming languages in equal footing Java and Objective-C, because Apple wasn't sure if developers would be keen in using Objective-C, like on NeXTSTEP.
They created their own Java implementation, had Sun on stage at WWDC, additional runtime features for integration with OS X frameworks, ported WebObjects to Java.
Then the crowd assembled around Objective-C tooling and the rest is history.
