RestKit: how to map URL param to object attribute - objective-c

Question

I've got REST service method like this one
/GetOfficeDocument?officeId=259
which returns an array of documents. Document in the app is a NSManagedObject object that has relationship to an office. How can I map officeId param to office relationship of my Document?
I know I should override objectLoader:willMapData:, but I don't know what exactly should I do inside of this method. The documentation is useless.
UPD. The response of the server looks like this:
[{"AddedDate":"\/Date(1261484400000+0400)\/","Title":"Some text","Uri":"\/Document\/News\/851"}]
As you see, officeId is not contained in response, only in URL. I can extract it in objectLoader:willMapData: using
[[[loader URL] queryParameters] objectForKey:#"officeId"]
but where should I put it next? Mappable data parameter is a mutable array, what should I place there? No idea.

Answer 1

You could try to inject the OfficeId value in each document item returned in the response like so:
- (void)objectLoader:(RKObjectLoader *)loader willMapData:(inout __autoreleasing id *)mappableData
{
NSString *officeId = [[[loader URL] queryParameters] objectForKey:#"officeId"];
NSMutableArray *newMappableData = [[NSMutableArray alloc] initWithCapacity:[*mappableData count]];
for (NSDictionary *documentDict in *mappableData)
{
NSMutableDictionary = newDocumentDict = [documentDict mutableCopy];
[newDocumentDict setObject:officeId forKey:#"OfficeId"];
[newMappableData addObject:newDocumentDict];
}
*mappableData = newMappableData;
}
And use something similar to the following in your Document mapping:
[documentMapping mapAttributes:#"AddedDate", #"Title", #"Uri", #"OfficeId", nil];
[documentMapping mapKeyPath:#"" toRelationship:#"office" withMapping:officeMapping];
[documentMapping connectRelationship:#"office" withObjectForPrimaryKeyAttribute:#"OfficeId"];

Answer 2

I usually add the RKObjectMapping to the managedObject class
Add this to your Document.h
+ (RKObjectMapping *)objectMapping;
Add this method to your Document.m
+ (RKObjectMapping *)objectMapping {
RKManagedObjectMapping *mapping = [RKManagedObjectMapping mappingForClass:[self class] inManagedObjectStore:[[RKObjectManager sharedManager] objectStore]];
mapping.primaryKeyAttribute = #"word";
[mapping mapKeyPath:#"word" toAttribute:#"word"];
[mapping mapKeyPath:#"min_lesson" toAttribute:#"minLesson"];
}
Off course you should change the key paths to your Document object properties. each pair is the name of the key on the server responds and it's corresponded keyPath on your managedObject.
Then when you initialize the objectManager you can set the mapping for each managedObject you have.
RKManagedObjectStore *store = [RKManagedObjectStore objectStoreWithStoreFilename:databaseName usingSeedDatabaseName:seedDatabaseName managedObjectModel:nil delegate:self];
objectManager.objectStore = store;
//set the mapping object from your Document class
[objectManager.mappingProvider setMapping:[SRLetter objectMapping] forKeyPath:#"Document"];
YOu can find a great tutorial here - RestKit tutorial. In the middle of the article you will find data about mapping.