How to deal with embedded arrays for json formatting in objective-c

Question

I have a dictionary called array:

     {
        "encoding": "320", 
        "format": "MP3", 
        "media": "CD", 
        "name": "foo", 
        "remaster_title": ""
    }, 
    {
        "encoding": "V0 (VBR)", 
        "format": "MP3", 
        "media": "CD", 
        "name": "bar", 
        "remaster_title": ""
    }, 
    {
        "encoding": "Lossless", 
        "format": "FLAC", 
        "media": "CD", 
        "name": "bar", 
        "remaster_title": "hoho"
    }

I want to separate these so that they are unique. For example there should only be one name so there will be two sections: foo and bar.

Then within each name (foo or bar) there should be the remaster_title (for foo: and bar both: and hoho)....

This should be in the order: name > remaster_title > media > format > encoding.

I think this would work if I could have a format similar to:

music[name][remaster_title][media][format] = encoding

so all the keys would then merge?

I have tried:

+(NSMutableDictionary*)handleReturnedArtistJson:(NSDictionary*)json{
    NSMutableDictionary *music = [[NSMutableDictionary alloc] init];
    for(NSDictionary *result in json[@"response"][@"group"]) {
        NSString* release_type = result[@"releaseType"];
        NSString* name = result[@"groupName"];

        if (![release_type  isEqual: @"Compilation"]){
            for (NSDictionary *subgroup in result[@"subgroup"]){
                NSString* media = subgroup[@"media"];
                NSString* remaster_title = subgroup[@"remasterTitle"];
                NSString* format = subgroup[@"format"];
                NSString* encoding = subgroup[@"encoding"];

                music[name][remaster_title][media][format] = encoding;
            }
        }
    }
    return music;
}

but NSLog(@"%@",music); returns nothing.

I don't see why you want all the nested dictionaries, why not just have something like {name:{remastered_title1:{"encoding":...,"format":...,"media":...}, remasted_title2:{...}}, name2:...} ? — Tadhg McDonald-Jensen
– Tadhg McDonald-Jensen, Commented Aug 30, 2016 at 16:53
As Tadhg has said, is there a reason you need it in a multi-nested dictionary? Can data be passed to your app in that nested format, if so you could potentially use Mantle, I can provide an example of this, if that's what you're looking for. — JingJingTao
– JingJingTao, Commented Sep 6, 2016 at 21:51
I just want to be able to iterate through each of the arrays within each array :) I am so confused about the structure! — maxisme
– maxisme, Commented Sep 7, 2016 at 8:33

Alex Nolasco · Accepted Answer · 2016-09-08 01:03:28Z

The comment area is too small to ask a few questions, but let's assume a few things. You want to parse the JSON into an object tree. Let's see if this code can help.

#import <Foundation/Foundation.h>

typedef NSMutableDictionary<NSString*, NSString*> formatDictionary;
typedef NSMutableDictionary<NSString*, formatDictionary*> mediaDictionary;
typedef NSMutableDictionary<NSString*, mediaDictionary*> titleDictionary;
typedef NSMutableDictionary<NSString*, titleDictionary*> nameDictionary;

@interface DataSource : NSObject
- (nameDictionary*)parseJSONFile:(NSString *)jsonFile error:(NSError *__autoreleasing *)outError;
@end

Implementation

@implementation DataSource

- (NSString *)valueOrDefaultFromDictionary:(NSDictionary *) dictionary forKey: (NSString *) key
{
    NSString * value = dictionary[key];
    if (![value length]) {
        return @"";
    }
    return value;
}

- (NSArray *)jsonToArray:(NSString *)jsonFile error:(NSError *__autoreleasing *)outError
{
    NSString *path  = [[NSBundle mainBundle] pathForResource:jsonFile ofType:@"json"];
    NSString *jsonString = [[NSString alloc] initWithContentsOfFile:path encoding:NSUTF8StringEncoding error:nil];
    NSError *jsonError;
    NSArray *jsonDataArray = [NSArray new];
    jsonDataArray = [NSJSONSerialization JSONObjectWithData:[jsonString dataUsingEncoding:NSUTF8StringEncoding] options:kNilOptions error:&jsonError];

    if (jsonDataArray == nil) {
        if (outError) {
            *outError = [NSError errorWithDomain:@"yourdomain" code:-42 userInfo:@{NSUnderlyingErrorKey: jsonError}];
        }
        return nil;
    }
    return jsonDataArray;
}


- (nameDictionary*)parseJSONFile:(NSString *)jsonFile error:(NSError *__autoreleasing *)outError
{
    NSArray * jsonDataArray = [self jsonToArray:jsonFile error:outError];
    if (!jsonDataArray) {
      return nil;
    }
    nameDictionary* music = [nameDictionary new];

    [jsonDataArray enumerateObjectsUsingBlock:^(id _Nonnull obj, NSUInteger idx, BOOL * _Nonnull stop) {
        NSString * name = [self valueOrDefaultFromDictionary:obj forKey:@"name"];
        NSString * title = [self valueOrDefaultFromDictionary:obj forKey:@"remaster_title"];
        NSString * media = [self valueOrDefaultFromDictionary:obj forKey:@"media"];
        NSString * format = [self valueOrDefaultFromDictionary:obj forKey:@"format"];
        NSString * encoding = [self valueOrDefaultFromDictionary:obj forKey:@"encoding"];
        music[name] = [@{title: [@{media: [@{format:encoding} mutableCopy] } mutableCopy] } mutableCopy];
    }];
    return music;
}
@end

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