How to map JSON data object inside an object?

Question

I'm trying to fetch some data from a API call and map those objects to a model object. In my case I have an object inside an object. This is working and received JSON. And it's mapping fine with the very first object. In my JSON I have an array and another array inside it. So I did the following to get this done.

Object mapping

+(NSArray *)fromJSON:(NSDictionary *)objectNotation error:(NSError *__autoreleasing *)error{
    NSError *localError = nil;

    NSDictionary *parsedObject = [[NSDictionary alloc] initWithDictionary:objectNotation];

    if (localError != nil) {
        *error = localError;
        return nil;
    }
    NSMutableArray *posts = [[NSMutableArray alloc] init];

    NSArray *results = [parsedObject valueForKey:@"data"];
    NSLog(@"Count %lu", (unsigned long)results.count);

    for (NSDictionary *groupDic in results) {
        Post *post = [[Post alloc] init];
        post.postBody = [NSMutableArray array];

        for (NSString *key in groupDic) {
            if ([post respondsToSelector:NSSelectorFromString(key)]) {
                [post setValue:[groupDic valueForKey:key] forKey:key];
            }
        }
        [posts addObject:post];
    }
    return posts;
}

This one makes multiple metadata than I expected because of the for loop.

Model classes

@interface OCPost : NSObject
@property(nonatomic) NSInteger postId;
@property(nonatomic) NSInteger userId;
@property(nonatomic) NSInteger points;
@property(strong, nonatomic) NSMutableArray *body;
@end

I want to map the body array with array of Body objects. In my body class

@interface Body : NSObject
@property (strong, nonatomic) NSString *value;
@property (strong, nonatomic) NSString *name;
@property (strong, nonatomic) NSMutableArray *metaData;
@end

And also the metadata should be map with the following object.

@interface MetaData : NSObject
@property (strong, nonatomic) NSString *title;
@property (strong, nonatomic) NSString *metaDataDescription;
@end

How may I make an object like,

Post
  |_Body1
  |  |_MetaData1
  |  |_MetaData2
  |  |_MetaData3
  |_Body3
  |  |_MetaData1
  |  |_MetaData2

Please help.

JSON

{
   "message": "Post ",
   "data": [
      {
        "postId": 1,
        "timestamp": "2016-06-14 22:37:02",
        "body": [
          {
            "textId": 1,
            "type": "link",
            "deleting": false,
            "metaData": [
          {
            "metadataId": 1,
            "type": "text",
            "value": "under "
          }
          ]
        },
        {
           "textId": 2,
           "type": "department",
           "deleting": false,
           "metaData": [
              {
                "metadataId": 2,
                "type": "text",
                "value": "under "
              }
           ]
        }
      ]
    }
  ]
}

have you checked up [mantle](https://github.com/Mantle/Mantle)? — Bartu, Jun 15 '16 at 22:58
yes. i tried. But didn't solve my problem. Then I switched to this one.. — codebot, Jun 15 '16 at 23:05
You also checked out [this](http://stackoverflow.com/questions/13883693/how-to-specify-child-objects-type-in-an-nsarray-with-mantle) feature? — Bartu, Jun 15 '16 at 23:18
You could try the JSONModel library, it allows for what you are trying to do. [link](https://github.com/icanzilb/JSONModel/blob/master/README.md#magical-data-modelling-framework-for-json) — Dennis W., Jun 16 '16 at 04:05
Nothing complex, value for key data is an array of bodies, each body has a value for key metadata which is array too. You should iterate over each array and create body object and metadata object. — Evgeny Karkan, Jun 18 '16 at 06:35

Evgeny Karkan · Accepted Answer · 2016-06-18T12:38:44.583

Ok, you can parse JSON and map it to your data models manually.
Here is how you can do it:

+(NSArray *)fromJSON:(NSDictionary *)objectNotation error:(NSError *__autoreleasing *)error{
    NSError *localError = nil;

    NSDictionary *parsedObject = [[NSDictionary alloc] initWithDictionary: objectNotation];

    if (localError != nil) {
        *error = localError;
        return nil;
    }
    NSMutableArray *posts = [[NSMutableArray alloc] init];

    NSArray *results = [parsedObject valueForKey:@"data"];
    NSLog(@"Count %lu", (unsigned long)results.count);

    for (NSDictionary *groupDic in results) {
        OCPost *post = [[OCPost alloc] init];
        post.body    = [NSMutableArray array];

        //1. Parse bodies
        NSArray *bodies = groupDic[@"body"];

        for (NSDictionary *aBody in bodies) {
            Body *body    = [[Body alloc] init];
            body.value    = aBody[@"textId"];
            body.name     = aBody[@"type"];
            body.metaData = [@[] mutableCopy];

            //2. Parse metadatas
            NSArray *metadatasOfBody = aBody[@"metaData"];

            for (NSDictionary *aMetadata in metadatasOfBody) {
                MetaData *metadata           = [[MetaData alloc] init];
                metadata.title               = aMetadata[@"type"];
                metadata.metaDataDescription = aMetadata[@"value"];

                //3. Add metadata to body
                [body.metaData addObject:metadata];
            }

            //4. Add body to post
            [post.body addObject: body];
        }

        //Logs to check post body and body metadata
        NSLog(@"post %@", post);
        NSLog(@"post body %@", post.body);

        for (Body *body in post.body) {
            NSLog(@"post body metadata %@", body.metaData);
        }

        //5. Add post to posts
        [posts addObject: post];
    }

    //Log to check return posts
    NSLog(@"posts %@", posts);

    return posts;
}

To test it you can represent your JSON as NSDictionary, like this:

- (NSDictionary*) aJSON
{
    return @{
        @"message": @"Post ",
        @"data": @[
                 @{
                 @"postId": @1,
                 @"timestamp": @"2016-06-14 22:37:02",
                 @"body": @[
                          @{
                          @"textId": @1,
                          @"type": @"link",
                          @"deleting": @false,
                          @"metaData": @[
                                       @{
                                       @"metadataId": @1,
                                       @"type": @"text",
                                       @"value": @"under "
                                       }
                                       ]
                          },
                          @{
                          @"textId": @2,
                          @"type": @"department",
                          @"deleting": @false,
                          @"metaData": @[
                                       @{
                                       @"metadataId": @2,
                                       @"type": @"text",
                                       @"value": @"under "
                                       }
                                       ]
                          }
                          ]
                 }
                 ]
        };
}

Replace objectNotation with [self aJSON] to be able test mapping without calling the server API, or of course, call server API endpoint, and try to test with response JSON.

How to map JSON data object inside an object?

1 Answers1