[问题记录]Property with 'retain (or strong)' attribute must be of object type

引用第三方开源库"Reachability.h"，编译的时候报错：

Property with 'retain (or strong)' attribute must be of object type

发现错误是在：

@property (nonatomic, strong) dispatch_queue_t reachabilitySerialQueue;

搜索了一番，原来这是因为SDK低于6.0时，dispatch_queue_t ARC没有托管，出现错误

只需将报错这一段修改为：

#if OS_OBJECT_USE_OBJC

@property (nonatomic, strong)
dispatch_queue_t reachabilitySerialQueue;

#else

@property (nonatomic, assign)
dispatch_queue_t reachabilitySerialQueue;

#endif

即可解决问题！