      
      - SeeAlso: dispatch_get_global_queue
     */
-    class func userInteractiveQueue() -> dispatch_queue_t {
+    static func userInteractiveQueue() -> dispatch_queue_t {
         return dispatch_get_global_queue(QOS_CLASS_USER_INTERACTIVE, 0)
     }
 


     - SeeAlso: dispatch_get_global_queue
     */
    class func backgroundQueue() -> dispatch_queue_t {
        return dispatch_get_global_queue(QOS_CLASS_BACKGROUND, 0)
    }
}

// MARK: - DSL for GCD queues

/**
`GCD` is an empty struct with convenience static functions to get `dispatch_queue_t` of different quality of service classes, as provided by `dispatch_get_global_queue`.

    let utilityQueue = GCD.utilityQueue()

- SeeAlso: Grand Central Dispatch
*/
private struct GCD {

    /**
     Convenience function for `dispatch_get_main_queue()`.
