Create a CurrentValueSubject from another CurrentValueSubject

Question

I have a CurrentValueSubject in an object and I want another CurrentValueSubject to copy the changes of the first one.

I can't find a way of easily doing that without having to do something like this:

subjectA.assign(to: \.value, on: subjectB).store(in: &cancelables)

It would be nice to be able to initialize the subjectB using subjectA. Is there a way of doing something like that?

Edit: For example I was thinking it would be great to be able to do something like:

let subjectB = CurrentValueSubject(from: subjectA)

Answer 1

I would just have the second publisher be a subscriber to the first publisher. Example:

let pub1 = CurrentValueSubject<String,Never>("howdy")
lazy var pub2 : AnyPublisher<String,Never> = {
    self.pub1.eraseToAnyPublisher()
}()

Example of usage:

    pub1.sink {print($0)}.store(in: &storage)
    pub2.sink {print($0)}.store(in: &storage)
    delay(1) {
        self.pub1.send("hey")
        delay(2) {
            self.pub1.send("ho")
        }
    }

Output:

howdy
howdy
[delay]
hey
hey
[delay]
ho
ho

So both publishers are giving out the same value, which seems to be what you want.