Syncronize.swift

import Foundation

/// Protocol for NSLocking objects that also provide tryLock()
public protocol TryLockable: NSLocking {
  func `try`() -> Bool
}

// These Cocoa classes have tryLock()
extension NSLock: TryLockable {}
extension NSRecursiveLock: TryLockable {}
extension NSConditionLock: TryLockable {}


/// Protocol for NSLocking objects that also provide lockBeforeDate()
public protocol BeforeDateLockable: NSLocking {
  func lock(before limit: Date) -> Bool
}

// These Cocoa classes have lockBeforeDate()
extension NSLock: BeforeDateLockable {}
extension NSRecursiveLock: BeforeDateLockable {}
extension NSConditionLock: BeforeDateLockable {}

func synchronize<L: NSLocking, T>(sync: L, action: () throws -> T ) rethrows -> T {
  sync.lock()
  defer { sync.unlock() }
  return try action()
}