Swift3.0で `dispatch_async` が使えなくなると聞いて

DispatchQueueSwift3.swift

// Swift2.x
dispatch_async(dispatch_get_main_queue()) { [weak self]() in
    if let weakSelf = self {
        weakSelf.tableView.reloadData()
    }
}

//Swift3.0
DispatchQueue.main.async { [weak self] in
    if weakSelf = self {
        self.tableView.reloadData()
    }
}