RestKit POST-Mapping issue - ios

Question

I've got a problem with a POST-Mappping in RestKit. Basically my application needs to send a JSON-file to a server which expects the JSON to look exactly like the following example:
{
"ddata": {
"mLoad": {
"value": 13,
"unit": "%"
},
"cLoad": {
"value": 25,
"unit": "%"
}
},
"dm": "0815",
"vin": "VAPP",
"ts": "2014-09-24"
}
Unfortunately I'm not able to create a Mapping with RestKit which generates me a JSON that matches this format. Here's how the JSON looks at the moment:
{
"ddata" : [
{
"mLoad" : {
"unit" : "%",
"value" : "25"
}
},
{
"cLoad" : {
"unit" : "%",
"value" : "37"
}
}
],
"ts" : "2014-09-24",
"vin" : "VAPP",
"dm" : "0815"
}
As you can see in the result the ddata stuff is written as an array. Furthermore the outer { } of each "object" is too much.
Following my classes and the Mapping:
Mapping Class
#interface TopMapping : NSObject
#property NSString *dm;
#property NSString *vin;
#property NSString *ts;
#property NSSet *ddata;
#end
SubMapping Class
#interface SubMapping : NSObject
#property NSString *object;
#property NSString *value;
#property NSString *unit;
#end
Actual mapping
RKObjectMapping *mapping = [RKObjectMapping mappingForClass:[TopMapping class]];
[mapping addAttributeMappingsFromDictionary:#{
#"dm": #"dm",
#"vin": #"vin",
#"ts": #"ts"
}];
RKObjectMapping *subMapping = [RKObjectMapping mappingForClass:[SubMapping class]];
[subMapping setForceCollectionMapping:YES];
[subMapping addAttributeMappingFromKeyOfRepresentationToAttribute:#"object"];
[subMapping addAttributeMappingsFromDictionary:#{
#"(object).value" : #"value",
#"(object).unit" : #"unit"
}];
[mapping addPropertyMapping:[RKRelationshipMapping relationshipMappingFromKeyPath:#"ddata" toKeyPath:#"ddata" withMapping:subMapping]];
Can anyone tell me what I need to change in order to get the desired result? Thanks in advance. (I've been struggling with this issue for days)

Answer 1

Check NSSet manual
You need to use NSDictionary instead of NSSet.