Unable to retrieve data with RestKit because class is not key value coding compliant - restkit

Question

I am writing a simple Multiple choice question for iOS.
I want to create an API so that I can retrieve the questions and store the answers of the users. I use django and tastypie for the backend.
I use this function to load the quesion in my app :
- (void)loadQuestion
{
RKObjectMapping* questionMapping = [RKObjectMapping mappingForClass:[Question class]];
[questionMapping addAttributeMappingsFromDictionary:#{
#"question": #"question",
}];
RKResponseDescriptor *responseDescriptor = [RKResponseDescriptor responseDescriptorWithMapping:questionMapping pathPattern:nil keyPath:#"question" statusCodes:RKStatusCodeIndexSetForClass(RKStatusCodeClassSuccessful)];
NSURL *URL = [NSURL URLWithString:#"http://127.0.0.1:8000/api/v1/question/2/?format=json"];
NSURLRequest *request = [NSURLRequest requestWithURL:URL];
NSLog(#"request : %#", request);
RKObjectRequestOperation *objectRequestOperation = [[RKObjectRequestOperation alloc] initWithRequest:request responseDescriptors:#[responseDescriptor]];
[objectRequestOperation setCompletionBlockWithSuccess:^(RKObjectRequestOperation *operation, RKMappingResult *mappingResult) {
RKLogInfo(#"Load collection of Articles: %#", mappingResult.array);
} failure:^(RKObjectRequestOperation *operation, NSError *error) {
RKLogError(#"Operation failed with error: %#", error);
}];
[objectRequestOperation start];
}
Here is my question.h :
#import <Foundation/Foundation.h>
#interface Question : NSObject
#property (strong) NSString *question;
#end
And my question.m
#implementation Question
#synthesize question = _question;
#end
The JSON is the following :
{
"chapter": "/api/v1/chapter/2/",
"id": 2, "
pub_date": "2013-04-25T19:23:42.930097",
"question": "Quelle est la capitale de ce pays : Emirats Arabes Unis ?",
"resource_uri": "/api/v1/question/2/"
}
And the tastypie API is :
from tastypie.resources import ModelResource
from tastypie import fields
from .models import Question, Chapter
class ChapterResource(ModelResource):
class Meta:
queryset = Chapter.objects.all()
resource_name = 'chapter'
class QuestionResource(ModelResource):
chapter = fields.ForeignKey(ChapterResource, 'chapter')
class Meta:
queryset = Question.objects.all()
resource_name = 'question'
The error i get is :
Terminating app due to uncaught exception 'NSUnknownKeyException', reason: '[<__NSCFString 0x76b3030> valueForUndefinedKey:]: this class is not key value coding-compliant for the key question.'
I read https://github.com/RestKit/RestKit/wiki/Object-Mapping but did not find what I am doing wrong.
What is wrong with my class ?

Answer 1

Try turning on trace logging to get more details about what's happening with the mapping:
RKLogConfigureByName("RestKit/ObjectMapping", RKLogLevelTrace);
That said, I'm not sure it's a problem with the mapping. The exception is thrown while trying to read the question from a string object. RestKit shouldn't be doing that based on your use case. So, you need to add a breakpoint on all exceptions so you can see the full stack trace and work out what's going on: Xcode adding an exception breakpoint.
Looking at your JSON and mapping spec it seems ok.