title: *** Assertion failure in -[RKObjectMapping addPropertyMapping:] crash in ios
body: <p>just started few days back with RestKit,
  need your review, where i am wrong..
  getting crash in ios app: *** Assertion failure in -[RKObjectMapping addPropertyMapping:]</p>
  
  <p>@interface VGShowCheckIn : NSObject</p>
  
  <p>@property (nonatomic,strong) NSNumber * ad_units;</p>
  
  <p>@property (nonatomic,strong) VGShowDetails * program;</p>
  
  <p>@interface VGShowDetails : NSObject</p>
  
  <p>@property (copy, nonatomic)     NSString            *programTitle;</p>
  
  <p>@property (copy, nonatomic)     NSString            *showId;</p>
  
  <p>=======</p>
  
  <p>RKObjectMapping *checkinMapping = [RKObjectMapping mappingForClass:[VGShowCheckIn class]];</p>
  
  <pre><code>[checkinMapping addAttributeMappingsFromDictionary:@{
  
                                                    @"ad_units" : @"ad_units",
  
                                                    @"program" : @"program"
  
                                                    }];
  
  
  
  
  
  RKObjectMapping *showMapping = [RKObjectMapping mappingForClass:[VGShowDetails class]];
  
  [showMapping addAttributeMappingsFromDictionary:@{
  
                                                    @"id"                                         :   @"showId",
  
                                                    @"title"                      :   @"programTitle",
  
                                                    }];
  </code></pre>
  
  <p>and app is crashing here :  [checkinMapping addPropertyMapping:[RKRelationshipMapping relationshipMappingFromKeyPath:@"program" toKeyPath:@"program" withMapping:showMapping]];</p>
  
  <p>and rest api response is:</p>
  
  <p>{</p>
  
  <pre><code>data =     {
  
      "ad_units" = 3;
  
      program =         {
  
          id = SH017232340000;
  
  
          title = "Man v. Food Nation";
      }
   }
  </code></pre>
  
  <p>}</p>
  
  <p>can any one guide me whats wrong in line: 
  [checkinMapping addPropertyMapping:[RKRelationshipMapping relationshipMappingFromKeyPath:@"program" toKeyPath:@"program" withMapping:showMapping]];</p>
  
  <p>crash issue: *** Assertion failure in -[RKObjectMapping addPropertyMapping:]</p>