How to update existing object with partial data in restkit? - ios

Question

I have get API which returns following data
{
"id": "45832",
"name": "test name",
"parentId":"xyz",
//other fields
}
I am able to save this data using restkit. I have another api to get changes which returns only updated fields. for example
{
"id": "45832",
"name": "test name2",
//other updated fields
}
I want this data to update existing object in db. But in my case it sets parentId and other missing attributes to null. I have set identification attribute in entity mapping.
EDIT:
Here is the class for managed object with entity mapping.
#import "ZEntity.h"
#import "ZContent.h"
#import "ZThumb.h"
#implementation ZEntity
#dynamic availableFrom;
#dynamic dueDate;
#dynamic entityId;
#dynamic name;
#dynamic perCompleted;
#dynamic state;
#dynamic type;
#dynamic thumb;
#dynamic contents;
#dynamic completedOn;
#dynamic totalScore;
#dynamic parent;
#dynamic settings;
+ (RKEntityMapping *)map{
RKEntityMapping *mapping = [RKEntityMapping mappingForEntityForName:NSStringFromClass([self class]) inManagedObjectStore:[RKManagedObjectStore defaultStore]];
mapping.persistentStore = [RKManagedObjectStore defaultStore].persistentStoreCoordinator.persistentStores.firstObject;
NSAssert(mapping.persistentStore != nil, #"Requires Persistent Store");
mapping.identificationAttributes = #[#"entityId"];
[mapping addAttributeMappingsFromDictionary:#{
#"id" : #"entityId",
#"type" : #"type",
#"name" : #"name",
#"dueDate" : #"dueDate",
#"state" : #"state",
#"availableFrom" :#"availableFrom",
#"percCompletion" : #"perCompleted",
#"completedOn" : #"completedOn",
#"totalScore" : #"totalScore"
}];
[mapping addPropertyMapping:[RKRelationshipMapping relationshipMappingFromKeyPath:#"thumb" toKeyPath:#"thumb" withMapping:[ZThumb map]]];
return mapping;
}
#end
Response descriptor
RKResponseDescriptor* entitiesD = [RKResponseDescriptor responseDescriptorWithMapping:[ZEntity map]
method:RKRequestMethodAny pathPattern:nil keyPath:#"objects"
statusCodes:RKStatusCodeIndexSetForClass(RKStatusCodeClassSuccessful)];
Json response
{
"total": 9,
"start": 1,
"count": 10,
"objects": [{
"id": "636488166759829858",
"type": "UPDATE",
"name": "copy1",
"canReattempt": false,
"score": 0,
"totalScore": 300,
"thumb": {
"id": "THUMB_QUPDATE4",
"expiry": 1472545125,
"url_180_120": "//s3-ap-southeast-1.amazonaws.com/mtgame-cdn.mindtickle.com/allaboard4.0/thumb/Q-Update-Thumbnail_04.png?AWSAccessKeyId=AKIAJYDLQOOEIA6NZLPQ&Expires=1472545125&Signature=To8a5SN7CoCiWDmmtXLkyANKulw%3D"
},
"dueDate": 1440845008,
"dueDateObj": {
"dueOn": 1440845008,
"dueDateExpiryAction": "NONE"
},
"state": "ACTIVE",
"percCompletion": 0.0,
"availableFrom": 1440585808,
"completedOn": 0,
"startTime": null,
"expiryTime": null,
"certificateCutOffScore": -1,
"lastPublishTime": 1440585653,
"completionCertificateEnabled": null
}]
}
In earlier calls I have set parent field for Entity class which is a relationship (I have verified this through sqlite browser too). In this json there is no parent returned. Once this call finished, parent is set to null. I have to keep existing parent value.