how to iterate nested dictionaries in objective-c

Question

Hi I have a json string converted unsing the JSON framework into a dictionary and I need to extract its content. How could I iterate to the nested dictionaries? I have already this code that allows me to see the dictionary:

NSDictionary *results = [responseString JSONValue]; 
NSMutableArray *catArray = [NSMutableArray array];

for (id key in results) {
    NSLog(@"key: %@, value: %@", key, [results objectForKey:key]);
    [catArray addObject:key];
    NSString *cat = key;
}

Could someone provide a sample on how to get to all the levels of the dic not using the name of the keys?

The result structure of the dic is like this: http://www.freeimagehosting.net/uploads/e7c020d697.png

alt text http://www.freeimagehosting.net/uploads/e7c020d697.png

thanks

ldj

Answer 1

I'm sure you have solved this at this point, but I found it convenient to write a recursive utility class function that recursively logs every key of a dictionary:

/**
 *  Recursively logs the keys and values of each object in the dictionary,
 *  along with the class of the value.
 *
 *  @param dict The dictionary to inspect
 */
+ (void)logDictionaryKeys:(NSDictionary*)dict {
    for (id key in dict) {
        if ([dict[key] isKindOfClass:[NSDictionary class]]) {
            [self logDictionaryKeys:dict[key]];
        }else {
            NSLog(@"Key: %@", key);
            NSLog(@"Value: %@ (%@)", dict[key], [dict[key] class]);
        }
    }

    return;
}

Answer 2

The header of the category:

#import <Foundation/Foundation.h>

@interface NSDictionary(Find)

-(id) findflat:(NSString*)keyToFind;

@end

The body:

#import "NSDictionary+Find.h"

@implementation NSDictionary(Find)

-(id) findflat:(NSString*)keyToFind{

    if([self objectForKey:keyToFind])
        return self[keyToFind];

    for(id key in self)
        if([[self objectForKey:key] isKindOfClass:[NSDictionary class]])
            return [[self objectForKey:key] findflat:keyToFind];


    return nil;
}

@end

Usage/Validation:

- (void)testExample {
// This is an example of a functional test case.
// Use XCTAssert and related functions to verify your tests produce the correct results.

NSDictionary *dic = @{};
XCTAssertNil([dic findflat:@"url"]);

dic = @{@"url":@"http://"};
XCTAssertEqual([dic findflat:@"url"],@"http://");

dic = @{@"other":@4};
XCTAssertNil([dic findflat:@"url"]);

dic = @{@"other":@4,@"url":@"http://"};
XCTAssertEqual([dic findflat:@"url"],@"http://");

dic = @{@"other":@4,@"sd":@"sdf"};
XCTAssertNil([dic findflat:@"url"]);

dic = @{@"other":@4,@"dic":@{@"url":@"http://"}};
XCTAssertEqual([dic findflat:@"url"],@"http://");

dic = @{@"other":@4,@"dic":@{@"sd":@2,@"url":@"http://"}};
XCTAssertEqual([dic findflat:@"url"],@"http://");

dic = @{@"other":@4,@"dic":@{}};
XCTAssertNil([dic findflat:@"url"]);

dic = @{@"other":@4,@"dic":@{@"dic":@{@"sd":@2,@"url":@"http://"}}};
XCTAssertEqual([dic findflat:@"url"],@"http://");

}

Answer 3

I have tried recursion and hope this could help.
P.S. This will return the first occurrence of the key.

+(id)getValue:(NSDictionary*)aDictionary forKey:(NSString *)aKey {
   id finalValue = nil;
   for (id key in [aDictionary allKeys]) {
      id value = aDictionary[key];
      if (value != nil && [key isEqualToString:aKey]) {
         finalValue = value;
         break;
      }
      else if ([value isKindOfClass:[NSDictionary class]]) {
       finalValue = [[self class] getValue:value forKey:aKey];
      }
   }
   return finalValue;
}

Answer 4

Try

for ((id) key in [results allKeys]) {
    NSLog(@"key: %@, value: %@", key, [results objectForKey:key]);
    [catArray addObject:key];
    NSString *cat = key;
}

Hope that helped.

EDIT: i'm not sure if i understand your structure correct, but i'm asuming you have some values in your dictionairy which are again dictionairies. if you want to interate through a dictionairy which is located inside another one you could do it like this:

for ((id) key in [results allKeys]) {
    id value = [results objectForKey:key];
    if ([value isKindOfClass:[NSDictionary class]]) {
        NSDictionary* newDict = (NSDictionary*)value;
        for ((id) subKey in [newDict allKeys]) {
            ...
        }
    }
}

Of couse if you know the specific key to your desired dictionairy, you can check for that instead of checking if the value is a dict. But maybe it's not a bad idea to check that in both cases...

Answer 5

You probably have to try recursive function.

-(void)recurse:(NSDictionary *)dict counter: (int*) i parent:(NSString *) parent{
    for (NSString* key in [dict allKeys]) {
        id value = [dict objectForKey:key];
        NSLog(@"%@ -> %@", parent, key);
        if ([value isKindOfClass:[NSDictionary class]]) {
            i++;
            NSDictionary* newDict = (NSDictionary*)value;
            [self recurse:newDict counter:i parent:key];
            i--;
        } else {
            //Do smthg
        }
    }
}

this will list all keys and its level.