RestKit Dynamic Mapping with heterogeneouse collections and Core Data - ios

Question

I have the following JSON structure which I want to map with RestKit in CoreData:
[
{
"id": 1,
"type": "folder",
"name": "Folder 1",
"children": [
{
"id": 1,
"type": "document",
"name": "Document 1"
},
{
"id": 2,
"type": "folder",
"name": "Folder 2",
"children": [
{
"id" : 2,
"type": "document",
"name": "Document 2"
}
]
}
]
}
]
It's a typical filesystem structure where a folder can contain other folders or documents.
I have two CoreData entities: Folder and Document.
The Folder entity has the following relationships:
Here is my Mapping Code:
RKEntityMapping* foldersMapping = [RKEntityMapping mappingForEntityForName:#"Folder" inManagedObjectStore:managedObjectStore];
foldersMapping.identificationAttributes = #[ #"objectId" ];
[foldersMapping addAttributeMappingsFromDictionary:#{#"id" : #"objectId",
#"name" : #"name"}];
RKEntityMapping* documentsMapping = [RKEntityMapping mappingForEntityForName:#"Document" inManagedObjectStore:managedObjectStore];
documentsMapping.identificationAttributes = #[ #"objectId" ];
[documentsMapping addAttributeMappingsFromDictionary:#{#"id" : #"objectId",
#"name" : #"name"}];
In my dynamic mapping I use the type of the object to decide if it is a document or a folder.
RKDynamicMapping* dynamicMapping = [RKDynamicMapping new];
[dynamicMapping setObjectMappingForRepresentationBlock:^RKObjectMapping *(id representation) {
if ([[representation valueForKey:#"type"] isEqualToString:#"Folder"]) {
return foldersMapping;
} else if ([[representation valueForKey:#"type"] isEqualToString:#"Document"]) {
return documentsMapping;
}
return nil;
}];
Now I added the dynamic mapping as relationship mapping to the folder mapping for the property children two times.
[foldersMapping addPropertyMapping:[RKRelationshipMapping relationshipMappingFromKeyPath:#"children" toKeyPath:#"children" withMapping:dynamicMapping]];
[foldersMapping addPropertyMapping:[RKRelationshipMapping relationshipMappingFromKeyPath:#"children" toKeyPath:#"documents" withMapping:dynamicMapping]];
And here is my Problem: All this works, but I got the following Warnings:
RestKitNesterFolderTestProject[9969:3a03] W
restkit.object_mapping:RKMappingOperation.m:554 WARNING: Failed
mapping nested object: The operation couldn’t be completed. (Cocoa
error 1550.)
I think the Problem is that I doubled the mapping for the relationship children, so RestKit tries to map each child two times, once as Folder and once as Document.
Any help is appreciated.