Atomic

Atomic.swift

import Dispatch

public final class Atomic<A> {

    private var _value: A
    private let queue: DispatchQueue

    public init(_ value: A, targetQueue: DispatchQueue? = nil) {
        _value = value
        queue = DispatchQueue(label: "Atomic", attributes: .concurrent, target: targetQueue)
    }

    public var value: A {
        return queue.sync { _value }
    }

    public func mutate(_ transform: (inout A) -> Void) {
        queue.sync(flags: .barrier) {
            transform(&_value)
        }
    }
}

extension Atomic: Equatable where A: Equatable {
    public static func ==(lhs: Atomic, rhs: Atomic) -> Bool {
        return lhs.value == rhs.value
    }
}

extension Atomic: Hashable where A: Hashable {
    public func hash(into hasher: inout Hasher) {
        hasher.combine(value)
    }
}

https://www.objc.io/blog/2018/12/18/atomic-variables/
https://www.objc.io/blog/2019/01/15/atomic-variables-part-2/
https://github.com/radianttap/Swift-Essentials/blob/master/Sources/Atomic.swift