[Pitch #4] Actors

[Douglas_Gregor]

@ruiba168

I am considering how to update my SDK to our customer when i use new concurrent model in the future.
Suppose current interface given to customer is as following:

class DataProvider {
func add(_ query: Query ) { }
}

I want change it from class to actor like following:

actor DataProvider {
func asyncAdd(_ query: Query ) { }
nonisolated func add(_ query: Query ){
await self.asyncAdd(query)
}
}

I think both old call like "provider.add(query)" and new style async call like "await provider.asyncAdd(query)" will work. So customer could leave their codes as before or take their time to port.

Is there something wrong？

It's close. You won't be able to await inside the add function, so you would need something more like this:

nonisolated func add(_ query: Query) {
  Task.runDetached {
    await self.asyncAdd(query)
  }
}

where Task.runDetached is part of the Structured Concurrency proposal under review now.

We've seen this come up a bit when porting code, and have a prototyped feature we call @asyncHandler that automates this a bit. It would allow your example to compress down to:

@asyncHandler func add(_ query: Query) {
  // body of your asyncAdd
}

Doug