[OC]Singleton的一种简便实现方式

static dispatch_queue_t xml_request_operation_processing_queue() {
static dispatch_queue_t af_xml_request_operation_processing_queue;
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
af_xml_request_operation_processing_queue = dispatch_queue_create("com.alamofire.networking.xml-request.processing", DISPATCH_QUEUE_CONCURRENT);
});

return af_xml_request_operation_processing_queue;
}

通过dispatch_once执行一次来保证af_xml_request_operation_processing_queue只有一次实例化的机会~

这个方法能够很好的在任何类中调起单例的时候使用~

下面为singleton启一个单独的线程

+ (void) __attribute__((noreturn)) networkRequestThreadEntryPoint:(id)__unused object {
do {
@autoreleasepool {
[[NSThread currentThread] setName:@"AFNetworking"];
[[NSRunLoop currentRunLoop] run];
}
} while (YES);
}

+ (NSThread *)networkRequestThread {
static NSThread *_networkRequestThread = nil;
static dispatch_once_t oncePredicate;
dispatch_once(&oncePredicate, ^{
_networkRequestThread = [[NSThread alloc] initWithTarget:self selector:@selector(networkRequestThreadEntryPoint:) object:nil];
[_networkRequestThread start];
});

return _networkRequestThread;
}