dispath_queue_t

dispath_queue_t

static dispatch_queue_t get_queue() {
    static dispatch_queue_t queue;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        dispatch_queue_attr_t attr = DISPATCH_QUEUE_SERIAL;
        if (NSFoundationVersionNumber >= NSFoundationVersionNumber_With_QoS_Available) {
            attr = dispatch_queue_attr_make_with_qos_class(attr, QOS_CLASS_BACKGROUND, 0);
        }
        queue = dispatch_queue_create("xxxx.yyy.zzz", attr);
    });
    return queue;
}