Swift only uses reference counting when working with objects; Structs are optimised using copy-on-write. There's currently work on implementing move and ownership semantics, similar to Rust, but opt-in rather than by default.
Swift structs are just like C structs (from a memory perspective). The copy-on-write thing is implemented manually by storing a private refcounted object in your struct. See the implementation of Array for example: https://github.com/apple/swift/blob/main/stdlib/public/core/...
There’s no magical copy-on-write mechanism at the language level.
I don't know why this is downvoted, it's true. There is no automatic copy on write optimization in Swift. It's a manual optimization that expensive types like Array implement manually.
meindnoch|3 years ago
Swift structs are just like C structs (from a memory perspective). The copy-on-write thing is implemented manually by storing a private refcounted object in your struct. See the implementation of Array for example: https://github.com/apple/swift/blob/main/stdlib/public/core/...
There’s no magical copy-on-write mechanism at the language level.
jshier|3 years ago