Experiment to implement bidirectional assignment of values using Combine/KVO publishers

NSObject+BidirectionalAssign.swift

import Combine
import Foundation

extension NSObjectProtocol where Self: NSObject {
    /// Assigns each unique element assigned to the key paths specified to the inverse object.
    func bidirectionallyAssign<Value: Equatable, B: NSObject>(
        from firstKeyPath: ReferenceWritableKeyPath<Self, Value>,
        to secondKeyPath: ReferenceWritableKeyPath<B, Value>,
        on otherObject: B
    ) -> [AnyCancellable] {
        return [
            publisher(for: firstKeyPath, options: [.initial, .new])
                .removeDuplicates()
                .assign(to: secondKeyPath, on: otherObject),
            otherObject.publisher(for: secondKeyPath, options: [.new])
                .removeDuplicates()
                .assign(to: firstKeyPath, on: self)
        ]
    }
}