RestKit 0.20: flattening the hierarchy with dynamic in JSON - ios

Question

I am using RestKit 0.20 and have a problem with mapping a JSON with hierarchy which contains dynamic keys into one Object.
The JSON looks like this:
{
"id": 42,
"name": "Name of this entity",
"specialDataMap": {
"2091:10": {
"id": 2091,
"type": "10",
"value": "1'509.49",
"name": "Name of special data type 10"
},
"2091:02" {
"id": 2091,
"type": "02",
"value": "5.5543",
"name": "Name of special data type 02"
}
}
}
and should be mapped with RestKit to such an object:
#interface InfoPoint : NSManagedObject
#property (nonatomic, retrain) NSString* identifier;
#property (nonatomic, retrain) NSString* name;
#property (nonatomic, retrain) NSString* valueOfType10;
#property (nonatomic, retrain) NSString* valueOfType02;
#end
As you can see, I do not want to create a relationship and store the special data into a separate object. It just doesn't make sense.
I want to assign the nested attributes into the InfoPoint object like all other attributes. Usually this would work with the key path of the nested objects but this path contains a dynamic part: "2091:10" is a combination of the id and the type where the id might change (was not my 'original' idea but I have to consume it).
I have read about the Handling Dynamic Nesting Attributes in the RestKit documentation. But I did not find if and how this might work together with nested attributes.
----- added as response to comment/question: ----
I have tried it as well with Dynamic Object Mapping. But it did not work because RestKit seems to have problem with the #"self" destination:
RKEntityMapping* type10Mapping = [RKEntityMapping mappingForEntityForName:#"InfoPoint" inManagedObjectStore:objectStore];
[type10Mapping addAttributeMappingsFromDictionary:#{
#"value": #"valueOfType10"}];
RKDynamicMapping* dynamicMapping = [[RKDynamicMapping alloc] init];
[mapping addPropertyMapping:[RKRelationshipMapping relationshipMappingFromKeyPath:#"specialDataMap" toKeyPath:#"self" withMapping:dynamicMapping]];
[dynamicMapping setObjectMappingForRepresentationBlock:^RKObjectMapping *(id representation) {
if ([[representation valueForKeyPath:#"type"] isEqualToString:#"10"]) {
return type10Mapping;
}
return nil;
}];

Answer 1

Your attempt at dynamic mapping isn't correct. You should supply the dynamic mapping to the response descriptor. The dynamic mapping should then create and return the appropriate mapping based on the keys it finds in the response. Something like (written free hand):
RKDynamicMapping* dynamicMapping = [[RKDynamicMapping alloc] init];
[dynamicMapping setObjectMappingForRepresentationBlock:^RKObjectMapping *(id representation) {
RKEntityMapping* typeMapping = [RKEntityMapping mappingForEntityForName:#"InfoPoint" inManagedObjectStore:objectStore];
[typeMapping addAttributeMappingsFromDictionary:#{
#"id" : #"identifier",
#"name": #"name",}];
NSDictionary *types = [representation valueForKeyPath:#"specialDataMap"];
for (NSString *key in types) {
NSDictionary *type = [[types objectForKey:key] objectForKey:#"type"];
if ([type isEqualToString:#"10"]) {
[typeMapping addAttributeMappingsFromDictionary:#{
[NSString stringWithFormat:#"specialDataMap.%#.value", key]: #"valueOfType10"}];
} else if ...
}
return typeMapping;
}];
RKResponseDescriptor *responseDescriptor = [RKResponseDescriptor responseDescriptorWithMapping:dynamicMapping
pathPattern:...
keyPath:nil
statusCodes:[NSIndexSet indexSetWithIndex:200]];