Synchronized.swift

import class Foundation.NSRecursiveLock

@dynamicMemberLookup @propertyWrapper
public final class Synchronized<Value> {
  
  public var wrappedValue: Value {
    get {
      lock()
      defer { unlock() }
      return value
    }
    set {
      lock()
      value = newValue
      unlock()
    }
  }
  private var value: Value
  private let lock: () -> Void
  private let unlock: () -> Void
  
  public convenience init(_ value: Value) {
    let recursiveLock = NSRecursiveLock()
    self.init(
      value,
      lock: recursiveLock.lock,
      unlock: recursiveLock.unlock
    )
  }
  
  public init(
    _ value: Value,
    lock: @escaping () -> Void,
    unlock: @escaping () -> Void
  ) {
    self.value = value
    self.lock = lock
    self.unlock = unlock
  }
  
  public subscript<T>(dynamicMember keyPath: KeyPath<Value, T>) -> T {
    get {
      lock()
      defer { unlock() }
      return value[keyPath: keyPath]
    }
  }
  
  public subscript<T>(dynamicMember keyPath: WritableKeyPath<Value, T>) -> T {
    get {
      lock()
      defer { unlock() }
      return value[keyPath: keyPath]
    }
    set {
      lock()
      value[keyPath: keyPath] = newValue
      unlock()
    }
  }
  
  public subscript<T: AnyObject>(dynamicMember keyPath: ReferenceWritableKeyPath<Value, T>) -> T {
    get {
      lock()
      defer { unlock() }
      return value[keyPath: keyPath]
    }
    set {
      lock()
      value[keyPath: keyPath] = newValue
      unlock()
    }
  }
  
  public func synchronizedAccess(_ closure: (inout Value) -> Void) {
    lock()
    closure(&value)
    unlock()
  }
}