Question

Is it possible to use key mapping with the following JSON structure or are we going to have to perform looping through values manually? Examples would be great. Their rest api doesn’t really map real world objects into a standard object structure, but just modeled after the XML attributes. 🙁

THINGS{
"lastModifiedDate": "2012-02-23-08.43.16.916000",
"myList": [{
  "attributeList": [
                    {"id": "","name": "Content Level","val": "Introductory"},
                    {"id": "","name": "Session Type","val": "Business Overview"},
                    {"id": "20110616053537016","name": "Speaker","val": "Jim Kim, Company1"},
                    {"id": "20110616053526559","name": "Speaker","val": "Bob Ironman, Company2"},
                    {"id": "20110803145027914","name": "Speaker","val": "Kristine Thomas, Company3"},
                    {"id": "","name": "Room","val": "Banyan"},
                    {"id": "","name": "Industry","val": "Cross Industry"},
                    {"id": "","name": "Loc","val": "Stadium I"},
                    {"id": "","name": "Topic Tag","val": "CMS Systems"},
                    {"id": "","name": "Status","val": "Accepted"},
                    {"id": "","name": "Sub-Event","val": "Leadership"},
                    {"id": "","name": "Session","val": "LVI"},
                    {"id": "","name": "SubTrack","val": "None"},
                    {"id": "","name": "Track","val": "Business Value Outsourcing"}
  ],

"active": true,
"desc": "This is a really cool thing",
"end": "16:00",
"id": "2011080146112",
"num": "1002A",
"start": "15:00",
"title": "The thing title"
  }
 ]
}

Answer 1

Yes it is possible with RestKit.

You can get all documentation you need reading this article from the official wiki and here you have an explanation for doing what you need. Hope this helps you!

First you will need three objects for each entity, one for the ThingsList, another for representing one Thing and another for representing one ThingAttribute. Let’s start by the most basic element, the ThingAttribute:

SOAttribute.h

#import <Foundation/Foundation.h>

@interface SOAttribute : NSObject{
    NSNumber *attributeId; //I use this nomenclature because the word 'id' is reserved, same for other objects.
    NSString *name;
    NSString *val;
}

@end

SOAttribute.m

@implementation SOAttribute
@end

This will let you to represent this part of the JSON:

{"id": "","name": "Content Level","val": "Introductory"}

Now we will define the Thing as follows:

SOThing.h

#import <Foundation/Foundation.h>

@interface SOThing : NSObject{

    NSArray *attributeList; //This represent the list of attributes defined before
    BOOL active;
    NSString *desc;
    NSString *title;
    NSString *end;
    NSString *start;
    NSString *num;
    NSNumber *thingId;

}

@end

SOThing.m

#import "SOThing.h"
@implementation SOThing
@end

As you can notice, you have to define the attributeList as an NSArray. RestKit automatically will know that you need to receive a list of attributes there. So we have defined the following structure:

{
    "attributeList": [...],
    "active": true,
    "desc": "This is a really cool thing",
    "end": "16:00",
    "id": "2011080146112",
    "num": "1002A",
    "start": "15:00",
    "title": "The thing title"
}

Finally you define the Thing List as follows:

SOThingList.h

#import <Foundation/Foundation.h>

@interface SOThingList : NSObject{
    NSDate *lastModifiedDate;
    NSArray *myList;
}
@end

SoThingList.m

#import "SOThingList.h"
@implementation SOThingList
@end

As before, we need a list of Things so we define myList as an NSArray.

Now, that was easy, here comes the magic where you indicate to RestKit how to map each entity.
On your App Delegate put the following code:

#import "SOThingList.h"
#import "SOThing.h"
#import "SOAttribute.h"

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions{


    RKObjectMappingProvider *mappingProvider = [RKObjectManager sharedManager].mappingProvider;

    RKObjectMapping *mappingForAttribute = [RKObjectMapping mappingForClass:[SOAttribute class]];
    //This can be mapped directly
    [mappingForAttribute mapAttributes:@"name",@"val", nil];
    //here you indicate the special case, id->attributeId on our object
    [mappingForAttribute mapKeyPath:@"id" toAttribute:@"attributeId"];
    //Set the new mapping into the mapping provider.
    [mappingProvider addObjectMapping:mappingForAttribute];

    RKObjectMapping *mappingForThing = [RKObjectMapping mappingForClass:[SOThing class]];
    //Same as before, these attributes can be mapped directly
    [mappingForThing mapAttributes:@"active",@"title",@"end",@"start",@"desc",@"num", nil];
    [mappingForThing mapKeyPath:@"id" toAttribute:@"thingId"];
    //Here I indicate that any object on NSArray on attributeList should be mapped using SOAttribute mapping defined above.
    [mappingForThing mapKeyPath:@"attributeList" toRelationship:@"attributeList" withMapping:mappingForAttribute];
    [mappingProvider addObjectMapping:mappingForThing];

    RKObjectMapping *mappingForThingsList = [RKObjectMapping mappingForClass:[SOThingList class]];
    [mappingForThingsList mapAttributes:@"lastModifiedDate", nil];
    [mappingForThingsList mapKeyPath:@"myList" toRelationship:@"myList" withMapping:mappingForThing];
    [mappingProvider addObjectMapping:mappingForThingsList];

}

After all the above, you can get your Thing List with the following method using blocks:

SomeObject.m

- (void) get: (NSString *) resourcePath onLoad:(RKObjectLoaderDidLoadObjectBlock) loadBlock onError:(RKRequestDidFailLoadWithErrorBlock)failBlock{

    RKObjectMapping *mapping = [[RKObjectManager sharedManager].mappingProvider objectMappingForClass:[SOThingList class]];
    [[RKObjectManager sharedManager] loadObjectsAtResourcePath:resourcePath usingBlock:^(RKObjectLoader* loader) {
        loader.objectMapping = mapping;
        loader.delegate = self;
        loader.onDidLoadObject = loadBlock;

        loader.onDidFailWithError = ^(NSError * error){
            NSLog(@"%@",error);
        };
        loader.onDidFailLoadWithError = failBlock;
        loader.onDidLoadResponse = ^(RKResponse *response) {
            //Do something
        };

    }];

}

And you use it like this…

[someObjectInstance get:@"http://mydomain.com/mywebservice/" onLoad:^(id object){
    SOThingList *thingList = (SOThingList *) object;
    //Do something with your shiny thingList
} onError:^(NSError *error) {
    //Display an error message :)
}];