***断言失败 - [RKObjectMapping addPropertyMapping：]在ios

Question

几天前用RestKit开始， 需要你的评论，我错了.. 在ios app中崩溃：***断言失败 - [RKObjectMapping addPropertyMapping：]

@interface VGShowCheckIn：NSObject

@property（非原子，强）NSNumber * ad_units;

@property（非原子，强）VGShowDetails *程序;

@interface VGShowDetails：NSObject

@property（copy，nonatomic）NSString * programTitle;

@property（copy，nonatomic）NSString * showId;

=======

RKObjectMapping * checkinMapping = [RKObjectMapping mappingForClass：[VGShowCheckIn class]];

[checkinMapping addAttributeMappingsFromDictionary:@{

                                                  @"ad_units" : @"ad_units",

                                                  @"program" : @"program"

                                                  }];





RKObjectMapping *showMapping = [RKObjectMapping mappingForClass:[VGShowDetails class]];

[showMapping addAttributeMappingsFromDictionary:@{

                                                  @"id"                                         :   @"showId",

                                                  @"title"                      :   @"programTitle",

                                                  }];

并且app崩溃了：[checkinMapping addPropertyMapping：[RKRelationshipMapping relationshipMappingFromKeyPath：@“program”toKeyPath：@“program”withMapping：showMapping]];

和休息api的回应是：

{

data =     {

    "ad_units" = 3;

    program =         {

        id = SH017232340000;


        title = "Man v. Food Nation";
    }
 }

}

任何人都可以指导我错误排队： [checkinMapping addPropertyMapping：[RKRelationshipMapping relationshipMappingFromKeyPath：@“program”toKeyPath：@“program”withMapping：showMapping]];

崩溃问题：***断言失败 - [RKObjectMapping addPropertyMapping：]