Swift Evolution Pitch: Modify Accessors
We propose the introduction of a new keyword,
modify, for implementing mutable computed properties and subscripts, alongside the currentgetandset.The bodies of
modifyimplementations will be coroutines, and they will introduce a new contextual keyword,yield, that will be used to yield a value to be modified back to the caller. Control will resume after theyieldwhen the caller returns.This
modifyfeature is currently available (but not supported) from Swift 5.0 as_modify, for experimentation purposes when reviewing this proposal.[…]
We cannot yield the value in the array’s buffer directly because it needs to be placed inside an optional. That act of placing inside the optional creates a copy.
We can work around this with some lower-level unsafe code. If the implementation of
Array.firsthas access to its underlying buffer, it can move that value directly into the optional, yield it, and then move it back[…] During the yield to the caller, the array is in an invalid state: the memory location where the first element is stored is left uninitialized, and must not be accessed. This is safe due to Swift’s rules preventing conflicting access to memory.
Previously:
- Efficiently Mutating Nested Swift Data Structures
- Fast Safe Mutable State in Swift 5
- Swift 5 Exclusivity Enforcement
4 Comments RSS · Twitter
I'm worried about the future of Swift. They seem to be constantly expanding the language to every direction. 2 keywords for this? I would expect something so heavyweight to be reserved for something bigger, like async/await.
I wish they would focus on fixing the bugs instead of chasing new things all the time. The compiler still crashes daily for me and I hit bugs in the language or compiler a few times a week.
My concern is that Swift feels like "C#, but harder". They've been rapidly evolving it by adding more features (though they still don't seem to have a good concurrency story?), but aside from A's quality concerns which I can't comment on, I worry that not enough effort is put into making the basics of the language more accessible to newcomers. It's supposed to be the mainstream way to build a macOS or iOS app, and it doesn't quite feel like it can scale down like that.
@Nick @A I do think this is an important addition to the language. But, yes, the compiler still seems buggy/crashy.
