由于sdk低于6.0时，dispatch_queue_t  ARC没有托管，出现提示错误，修改为：

#if OS_OBJECT_USE_OBJC@property (nonatomic, strong) dispatch_queue_t completionQueue;#else@property (nonatomic, assign) dispatch_queue_t completionQueue;#endif

 

#if OS_OBJECT_USE_OBJC@property (nonatomic, strong) dispatch_group_t completionGroup;#else@property (nonatomic, assign) dispatch_group_t completionGroup;#endif