Synchronized

Exposes Objective-C's @synchronized directive to Swift. Like the Objective-C directive, Synchronized acquires a mutex lock, runs some code, and releases the lock when the code completes or throws an exception.

Linking the Framework

Synchronized is available through CocoaPods. To install it, simply add the following line to your Podfile:

pod "Synchronized"

Once the framework is linked this Swift code should compile:

import Synchronized

let x = synchronized(NSObject()) { 0 }

Public API

public func synchronized(object: AnyObject, closure: () -> Void)

Usage:

synchronized(mutexObject) {
  // Code to run in your critical section
}

---

public func synchronized<T>(object: AnyObject, closure: () -> T) -> T

Usage:

let value = synchronized(threadUnsafeDictionary) {
  threadUnsafeDictionary[key]
}

Differences from @synchronized

Objective-C's @synchronized is a language-level directive and does not introduce a new function scope. This means that return statements cause the program to return from the surrounding function that contains the @synchronized directive.

- (void)returnDifferenceExample
{
    @synchronized {
        return;
    }
    NSLog(@"This line of code does not run.");
}

In contrast, Synchronized uses closures which do introduce a function scope. Returning from a closure passed to synchronized exits only the closure, not the surrounding function.

func returnDifferenceExample() {
    synchronized {
        return
    }
    println("This line of code does run.")
}

Synchronized's closures are annotated with the @noclosure attribute, which removes the need to access instance variables with self., so it is similar to Objective-C's @synchronized directive in this regard.