1 - GrandCentralSwift.swift

import Foundation

public let GCD_MAIN_QUEUE = dispatch_get_main_queue()
public let GCD_BACKGROUND_QUEUE = dispatch_get_global_queue(QOS_CLASS_BACKGROUND, 0)
public let GCD_LOW_PRIORITY_QUEUE = dispatch_get_global_queue(QOS_CLASS_UTILITY, 0)
public let GCD_DEFAULT_QUEUE = dispatch_get_global_queue(QOS_CLASS_DEFAULT, 0)
public let GCD_HIGH_PRIORITY_QUEUE = dispatch_get_global_queue(QOS_CLASS_USER_INITIATED, 0)

public func after(delay: NSTimeInterval, block: () -> ())
{
    dispatch_after(dispatch_time(DISPATCH_TIME_NOW, Int64(delay * Double(NSEC_PER_SEC))), dispatch_get_main_queue(), block);
}

public func usingMainQueue(block: () -> ())
{
    usingQueue(GCD_MAIN_QUEUE, block);
}

public func usingBackgroundQueue(block: () -> ())
{
    usingQueue(GCD_BACKGROUND_QUEUE, block);
}

public func usingQueue(queue: dispatch_queue_t, block: () -> ())
{
    dispatch_async(queue, block);
}

2 - Example.swift

// Old way

dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_BACKGROUND, 0), {
    self.measurements = self.getMeasurementData()
    dispatch_async(dispatch_get_main_queue(), {
        self.tableView.reloadData()
    })
})

dispatch_after(dispatch_time(DISPATCH_TIME_NOW, Int64(2.0 * Double(NSEC_PER_SEC))), dispatch_get_main_queue(), {
    if let photo = UIImage(named: "me") {
        self.uploadImage(photo)
    }
})

// ------------------------------------------------------------

// New way
usingBackgroundQueue {
    self.measurements = self.getMeasurementData()
    usingMainQueue {
        self.tableView.reloadData()
    }
}

after(2.0) {
    if let photo = UIImage(named: "me") {
        self.uploadImage(photo)
    }
}