I think optionals are my favorite feature. That may be due to me coming from a Java background (which also has optionals since 8, but I feel it's rather clumsy compared to Swift and other modern native languages).

By doing optional chaining you can do something like: if let name = result.person?.firstName { ... } which only evaluates firstName if person is not nil, and then stores the result in name which is immutable.

It's easier to avoid mutable code in Swift than in many other languages. For this reason I would love to start working with Swift on the backend at some point in the future.

I like extensions, being able to extend any class I want by just typing it into any file I want. This helps with iterative development and trying something out.

Speaking of iteratively, if I want to try something quick, I can also drop down to a shell and start the Swift REPL to experiment.

I like how built-in functions like zip and mapValues are available, so it in some ways has a Pythonic feel. I like the syntax of building strings by just taking a variable name and going let s = "Hi there \(name)!".

There are lots of other things I enjoy, such as subscripts (see why here: https://docs.swift.org/swift-book/LanguageGuide/Subscripts.h...) and

Some things I would like to see improved is Xcode itself and also Swift's capabilities in the backend.

Thanks for the answer!

I've been waiting impatiently for a better Swift backend ecosystem, because I'd love to use it for web development as well.

I’m having a great time in Vapor 3.

Vapor is pretty amazing. Super fast and pretty fun to work with; also a very friendly community. Ray Wenderlich’s team as well as Paul Hudson also have some great books on server-side Swift for those looking to learn this stuff.

As a mainly C# developer, it seems we have a lot of features in common!

yeah, string interpolation is such a killer feature. I love using it in Python 3.6.

not parent, but features of Swift that I _really_ miss when working in other languages are:

- rich enums - (https://appventure.me/2015/10/17/advanced-practical-enum-exa...) Much of my code is now encapsulated in the enum, where it logically belongs, instead of distributed throughout some class that consumes the enum.

- highly expressive pattern matching - (https://appventure.me/2015/08/20/swift-pattern-matching-in-d...) Swift's pattern matching is especially powerful with a switch statement. I frequently bundle multiple values into a tuple and switch across them, which allows me to flatten many if-else pyramids, and makes control flow more obvious up front.

- Optional - (https://developer.apple.com/documentation/swift/optional)

- Protocol extensions - (https://docs.swift.org/swift-book/LanguageGuide/Extensions.h...) Other languages use things like abstract classes or traits to implement this behavior, but I find protocols to be much more composable.

- The standard library - Swift's standard library is really well thought out. Many standard types have been built on top of highly reusable (and easy to reason about) types or interfaces that provide enormous utility when I adopt them in my custom types. Examples of this are: Codable (https://developer.apple.com/documentation/foundation/archive...), Equatable and Hashable (https://developer.apple.com/documentation/swift/adopting_com...)

There's more than that, and Swift is definitely not without it's shortcomings, but those features have fundamentally changed how I reason about code. I frequently find myself wishing I could reach for similar tools in other languages.

I agree with that list and I’d also add value types in structs. Getting rid of all the shared state that objects and reference types add has been a big win for stability and correctness in my apps. I’m getting out of iOS development in favor of the web but I’ll miss swift.

To add to the other good answers here: I love its succinctness. The syntax itself is succinct (but still extremely readable) and the pervasive availability of functional-style methods (map/filter/reduce/etc) make it easier to keep lots of code in your head and on your screen at one time, making it much easier to understand complex code.

Not OP, but if you look at Rust, take out the borrow checker and you basically have Swift. It's a nice combination of modern OO and functional language constructs that make it easy to write elegant abstractions.

Python like