iOS creating complex JSON - ios

Question

I have been struggling with this issue for some time now and I cant figure out why the JSON serialization is not working. What seems to be a simple task it taking way too long.
I have my model classes listed below. User object has NSArray of Education and Employment objects.
I am using RestKit and all of the relationships have been made and I can see that the dictionary of the parameters is being made the data is correct. In order to debug the issue further I am making JSON using the following code.
NSDictionary *parameters = [RKObjectParameterization parametersWithObject:self.user requestDescriptor:delegate.postUserRequestDescriptor error:&error];
// Serialize the object to JSON
BOOL isTurnableToJSON = [NSJSONSerialization
isValidJSONObject: parameters];
if(isTurnableToJSON){
NSData *JSON = [RKMIMETypeSerialization dataFromObject:parameters MIMEType:RKMIMETypeJSON error:&error];
}
isTurnableToJSON is always "NO". When I force creation of JSON I get the following error.
** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: 'Invalid type in JSON write (Education)'
The same error is also thrown for employment if I remove the relationship of Education with user.
Here is my user, education, and location models.
#interface User : NSObject
#property (strong, nonatomic) NSString *first_name;
#property (strong, nonatomic) NSString *middle_name;
#property (strong, nonatomic) NSString *last_name;
#property (strong, nonatomic) NSString *profile_picture;
#property (strong, nonatomic) NSString *display_name;
#property (nonatomic, strong) NSArray *education;
#property (nonatomic, strong) NSArray *employment;
#property (nonatomic, strong) NSMutableArray *skills;
#property (strong, nonatomic) NSString *about_you;
#end
#interface Education : NSObject
#property (nonatomic, strong) NSString *name;
#property (nonatomic, strong) NSString *graduation_date;
#property (nonatomic, strong) NSString *major;
#property (nonatomic, strong) NSString *degree;
#property (nonatomic, strong) Location *location;
#property (nonatomic) NSNumber *current;
#end
#interface Location : NSObject
#property (nonatomic, strong) NSString *city;
#property (nonatomic, strong) NSString *state;
#property (nonatomic, strong) NSString *country;
#end
At this point I am at lose of any ideas and any help would be appreciated.
Update: RestKit Relationship mapping.
RKObjectMapping *locationMap = [RKObjectMapping mappingForClass:(Location.class)];
[locationMap addAttributeMappingsFromDictionary:#{#"city":#"city",#"state":#"state",#"country":#"country"}];
RKObjectMapping *educationMap = [RKObjectMapping mappingForClass:(Education.class)];
[educationMap addAttributeMappingsFromDictionary:# { #"name":#"name",#"graduation_date":#"graduation_date",#"major":#"major", #"degree":#"degree",#"current":#"current"}];
[educationMap addPropertyMapping:[RKRelationshipMapping relationshipMappingFromKeyPath:#"location" toKeyPath:#"location" withMapping:locationMap]];
RKObjectMapping *employmentMap =[RKObjectMapping mappingForClass:(Employment.class)];
[employmentMap addAttributeMappingsFromDictionary:#{#"company":#"company",#"occupation":#"occupation", #"start_date":#"start_date",#"end_date":#"end_date",#"current":#"current"}];
RKObjectMapping *userPutRequestMapping = [RKObjectMapping requestMapping];
[userPutRequestMapping addAttributeMappingsFromDictionary:putUserMap];
[userPutRequestMapping addPropertyMapping:[RKRelationshipMapping relationshipMappingFromKeyPath:#"education" toKeyPath:#"education" withMapping:[educationMap inverseMapping]]];
[userPutRequestMapping addPropertyMapping:[RKRelationshipMapping relationshipMappingFromKeyPath:#"employment" toKeyPath:#"employment" withMapping:[employmentMap inverseMapping]]];
USER PUT REQUEST
[objectManager addRequestDescriptor:[RKRequestDescriptor requestDescriptorWithMapping:userPutRequestMapping
objectClass:[User class]
rootKeyPath:nil
method:RKRequestMethodPUT]];