[drewcrawford]

This is already being done.

Swift 4 (unreleased) has source compatibility with Swift 3 [0], so all Swift code working today should work in the next version, no migrator necessary.

Additionally, the goal of Swift 4 is to finalize the ABI. Once that is done, you can mix and match different Swift versions in the same project.

The real "problem" here is that Swift wants to be a "big" language, in the vein of C++ or Rust, as opposed to a "small" language like C or JS where you can read one book. (Swift does have a book, it's 1200 pages.) There's a lot of "stuff": a complex typesystem, many basetypes, generics, extensions, both static and dynamic dispatch, programmer-assisted memory management, closures, visibility, ephemerals, optionals, a mutability-based memory model, etc. etc.

Inevitably some of that stuff won't be quite right and so you have churn. But ideally you only need 10% of those (it's just that everybody needs a different 10%) and so the amount of churn you personally have to deal with should be low, and can be lower with the appropriate tooling.

[0] https://swift.org/blog/swift-4-0-release-process/

[1] https://github.com/apple/swift-evolution

[0x0]

I thought they announced swift 4 would not finalize the ABI after all? http://mjtsai.com/blog/2017/02/16/deferring-abi-stability-fr...

[Someone]

"Swift does have a book, it's 1200 pages."

It is an ePub, so your mileage may vary. On my iPad, it is 1077 in landscape, 892 in portrait (edit: playing with the font size in iBooks, I got it down to 484 pages while still being eminently readable for my myopic eyes)

More importantly, that ePub on my iPad shows only 16-ish on a page in landscape mode, 22-ish on portrait. A printed book probably would be around 300-400 pages.

In comparison, the PDF I have for "small" language ISO C 2011 has 701 pages, a draft of ECMA-262 for JavaScript 252.

[edblarney]

"Swift wants to be a "big" language"

My guess is that it is not ideological. Swift feels like it wants to be 'everything'.

Because of this, it's almost too much.

I want to like Swift, but I run into a lot of trouble with it.

The decision to be compatible with ObjC was one of the big issues: obviously, pragmatically, they felt that they just had to do it. In hindsight, I wonder if it would have been better to just have a clean break.

[fiedzia]

> In hindsight, I wonder if it would have been better to just have a clean break.

Language-wise - sure, it adds a lot of complexity. Platform-wise, they would risk people staying on what they had and ignoring Swift entirely, and that would mean Apple would need to support objective-c a lot longer than they want to.

[mpweiher]

>compatible with ObjC was one of the big issues

Considering that was going to be hard requirement, maybe the problem was introducing so many things that are so incompatible with ObjC? There are tons of ways you could vastly improve the programming experience without introducing all this incompatible stuff.

[hboon]

As noted in the first link above, source compatibility isn't kept with Swift 3->4 anymore. There are changes to the String APIs.

[mahyarm]

If your an objective-c programmer, a lot of swift concepts are very close to each other. Most of the time you just pick it up as you go along. In many ways it's a cleaned up objective-c.