Question

With the help of mja, I managed to successfully set up simple object mapping using RestKit and Objective-C. Please see my previous question here.

My next step was to attempt to deal with nested JSON in the same way.

My JSON looks like this, with the outer being a CandidatePhrase with some nested ‘Votes’:

{ "Id":33696,
"Phrase": "phrase",
"BadCount":0,
"Votes":[{"Id":447,"OriginalId":33696,"Votes":2,"Translation":"translation 1"},
{"Id":746,"OriginalId":33696,"Votes":1,"Translation":"translation 2"},
{"Id":747,"OriginalId":33696,"Votes":1,"Translation":"translation 3"}
]}

I created a relationship in my AppDelegate as follows:

[candidatePhraseMapping mapKeyPath:@"votes" toRelationship:@"vote" withMapping:voteMapping];

When I call make my request in my controller, I’m able to deal with the rest of the CandidatePhrase okay, but am not really sure how to map the nested ‘Vote’ objects into an array so I can use them in a TableView

(pseudo-code something like this…)

// Store the votes in an array
_votes = [[NSArray alloc] initWithObjects:myCandidatePhrase.votes, nil];

Here’s my CandidatePhrase Object

@interface CandidatePhrase : NSObject

@property (nonatomic, retain) NSNumber* ident;
@property (nonatomic, retain) NSNumber* badcount;
@property (nonatomic, retain) NSString* phrase;
@property (nonatomic, retain) NSArray* votes;

@end

and my Vote object

@interface Vote : NSObject

@property (nonatomic, retain) NSNumber* ident;
@property (nonatomic, retain) NSNumber* originalId;
@property (nonatomic, retain) NSNumber* votecount;
@property (nonatomic, retain) NSString* translation;

+ (id)voteWithTranslationId:(NSNumber *)ident translation:(NSString *)translation;

@end

Any help would be much appreciated.

EDIT

Below is my mapping code

// Votes Mapping

RKObjectMapping* voteMapping = [RKObjectMapping mappingForClass:[Vote class]];
[voteMapping mapKeyPath:@"Id" toAttribute:@"ident"];
[voteMapping mapKeyPath:@"OriginalId" toAttribute:@"originalId"];
[voteMapping mapKeyPath:@"Votes" toAttribute:@"votecount"];
[voteMapping mapKeyPath:@"Translation" toAttribute:@"translation"];

[[manager mappingProvider] addObjectMapping:voteMapping];

// Candidate Phrase Mapping
RKObjectMapping *candidatePhraseMapping = [RKObjectMapping mappingForClass:[CandidatePhrase class]];

[candidatePhraseMapping mapKeyPath:@"Id" toAttribute:@"ident"];
[candidatePhraseMapping mapKeyPath:@"Phrase" toAttribute:@"phrase"];
[candidatePhraseMapping mapKeyPath:@"BadCount" toAttribute:@"badcount"];

[candidatePhraseMapping mapKeyPath:@"Votes" toRelationship:@"votes" withMapping:voteMapping];

[[manager mappingProvider] addObjectMapping:candidatePhraseMapping];

For clarity also, here’s how I’m attempting to access the vote items on the controller

- (void)objectLoader:(RKObjectLoader*)objectLoader didLoadObject:(id)object 
{ 
    CandidatePhrase *myCandidatePhrase = (CandidatePhrase*)object;
    self.candidateText.text = myCandidatePhrase.phrase; <-- works fine

    _votes = [[NSArray alloc] initWithObjects:myCandidatePhrase.votes, nil];
    for (id o2 in _votes) { 
        //Vote *vote = o2; 
        NSLog(@"Item name: %@", o2); <-- sees object but crashes
    }

    NSLog(@"Votes: %@", myCandidatePhrase.votes); 
    _votes = [[NSArray alloc] initWithObjects:myCandidatePhrase.votes, nil];
     [_votesTableView reloadData];
 } 

and my table is binding with

Vote *vote = [_votes objectAtIndex:indexPath.row];
cell.textLabel.text = vote.translation;

Answer 1

You do not need to manually manage the nested NSArray. I believe the problem might be just a simple typo, as you map keyPath “votes”, but your json contain “Votes” with capital “V”.

[candidatePhraseMapping mapKeyPath:@"Votes" toRelationship:@"votes" withMapping:voteMapping];

If this doesn’t help feel free to leave a comment and update your question with voteMapping.

Also, the contents of the didLoadObject can be simplified:

//in .h file
@property (nonatomic, retain) NSArray* votes;

// in implementation
@synthesize votes;

...
- (void)objectLoader:(RKObjectLoader*)objectLoader didLoadObject:(id)object 
{ 
    CandidatePhrase *myCandidatePhrase = (CandidatePhrase*)object;
    self.candidateText.text = myCandidatePhrase.phrase;
    self.votes = myCandidatePhrase.votes;
}