RESTKIT .20.1 nested array with relationship mapping assistance - restkit-0.20

Question

I am having trouble with RESTKIT and mapping the following JSON via RESTKit .20.1. I have a nested JSON array and I am trying to map via the RelationshipMapper. I am able to map the 5 chart_data object successfully but the related nested chart_datatum objects do not map to the ChartDataDetails class. All of the properties are blank.
I would like the following object structure.
Alert Instance
Array of ChartData objects
Each ChartData object should contain 1 ChartDataDetails object <---- this object is blank
Please see the link at the bottom for the screenshot of the XCode Debugger for the current state.
Can someone please provide some assistance?
Thanks,
G
{
"alert_instance": {
"alert_template_id": 1,
"alert_time_period": "2013-05-29",
"chart_data": [
{
"chart_datum": {
"alert_instance_id": 1,
"chart_data_id": 1,
"chart_data_name": "provider_id",
"datatype": 1,
"chart_data_value": "1"
}
},
{
"chart_datum": {
"alert_instance_id": 1,
"chart_data_id": 1,
"chart_data_name": "Provider_name",
"datatype": 2,
"chart_data_value": "Stubbs, Drew"
}
},
{
"chart_datum": {
"alert_instance_id": 1,
"chart_data_id": 1,
"chart_data_name": "Posting_date",
"datatype": 3,
"chart_data_value": "05/12/2013"
}
},
{
"chart_datum": {
"alert_instance_id": 1,
"chart_data_id": 1,
"chart_data_name": "Charges",
"datatype": 5,
"chart_data_value": "229"
}
},
{
"chart_datum": {
"alert_instance_id": 1,
"chart_data_id": 1,
"chart_data_name": "Payments",
"datatype": 5,
"chart_data_value": "-1023.11"
}
}
]
}
Model classes
AlertInstance.h
#interface AlertInstance : NSObject
#property (nonatomic, copy) NSNumber* alertTemplateId;
#property (nonatomic, copy) NSDate* alertTimePeriod;
#property (nonatomic, retain) NSMutableArray* chartData;
#end
ChartData.h
#interface ChartData : NSObject
#property (nonatomic, retain) ChartDataDetails *chartDataDetails;
#end
ChartDataDetails.h
#interface ChartDataDetails : NSObject
#property (nonatomic, copy) NSNumber* chartDataId;
#property (nonatomic, copy) NSString* chartDataName;
#property (nonatomic, copy) NSNumber* chartDataType;
#property (nonatomic, copy) NSNumber* chartDataValue;
#end
code for mappings..
RKObjectMapping* chartDataDetailMapping = [RKObjectMapping mappingForClass:[ChartDataDetails class]];
[chartDataDetailMapping addAttributeMappingsFromDictionary:#{
#"chart_data_id": #"chartDataId",
#"chart_data_name": #"chartDataName",
#"datatype": #"chartDataType",
#"chart_data_value": #"chartDataValue",
}];
RKObjectMapping* chartDataMapping = [RKObjectMapping mappingForClass:[ChartData class]];
[chartDataMapping addAttributeMappingsFromDictionary:#{
#"chart_data":#"chartData"}];
RKObjectMapping* alertInstanceMapping = [RKObjectMapping mappingForClass:[AlertInstance class]];
[alertInstanceMapping addAttributeMappingsFromDictionary:#{
#"alert_template_id": #"alertTemplateId",
#"alert_time_period": #"alertTimePeriod",
}];
[alertInstanceMapping addPropertyMapping:[RKRelationshipMapping relationshipMappingFromKeyPath:#"chart_data"
toKeyPath:#"chartData"
withMapping:chartDataMapping]];
[alertInstanceMapping addPropertyMapping:[RKRelationshipMapping relationshipMappingFromKeyPath:#"chart_datum"
toKeyPath:#"chartDataDetails"
withMapping:chartDataDetailMapping]];
RKResponseDescriptor *responseDescriptor = [RKResponseDescriptor responseDescriptorWithMapping:alertInstanceMapping
pathPattern:nil
keyPath:#"alert_instance"
statusCodes:RKStatusCodeIndexSetForClass(RKStatusCodeClassSuccessful)];
NSURL *URL = [NSURL URLWithString:#"http://ideainnovationsmobiledev1.cloudapp.net:3000/alert_instances/1.json"];
NSURLRequest *request = [NSURLRequest requestWithURL:URL];
RKObjectRequestOperation *objectRequestOperation = [[RKObjectRequestOperation alloc] initWithRequest:request responseDescriptors:#[ responseDescriptor ]];
[objectRequestOperation setCompletionBlockWithSuccess:^(RKObjectRequestOperation *operation, RKMappingResult *mappingResult)
link to screen shot of the debugger
https://docs.google.com/file/d/0Bwaj6O1rXiKaeFIwT2s4Rm1Gb00/edit?usp=sharing
EDIT:
Ok I figured it out.
I needed to chain the ChartDetailsMapping to the ChartData as follows.
[chartDataMapping addPropertyMapping:[RKRelationshipMapping relationshipMappingFromKeyPath:#"chart_datum"
toKeyPath:#"chartDataDetails"
withMapping:chartDataDetailMapping]];
[alertInstanceMapping addPropertyMapping:[RKRelationshipMapping relationshipMappingFromKeyPath:#"chart_data"
toKeyPath:#"chartData"
withMapping:chartDataMapping]];