Xcode的#import比#include的好处是解决多重包含的问题，遇到了相互包含头文件的问题

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

解决方案就是在出错头文件中实现

@class 文件名;即可解决例如

#import#import#import "RACBaseViewModelService.h"

#import "RACNavigationImpl.h"

@class RACNavigationImpl;

@interface RACBaseViewModel : NSObject

/// nav

@property(nonatomic,strong) RACNavigationImpl *naviImpl;

文章参考链接

https://stackoverflow.com/questions/8828398/how-to-solve-this-error-property-with-retainor-strong-attribute-must-be-of