In-place removal of [NSNull null] values in collections.Useful when importing JSON data into realm-cocoa. Note that the whole structure must be Mutable (e.g. all child collections are NSMutableArray or NSMutableDictionary)

NSMutableDictionary+BVMNullReplacement.h

@import Foundation;

// In-place removal of [NSNull null] values
// Useful when importing into Realm
@interface NSMutableDictionary (BVMNullReplacement)
- (void)bvm_removeNulls;
@end

// In-place removal of [NSNull null] values
// Useful when importing into Realm
@interface NSMutableArray (BVMNullReplacement)
- (void)bvm_removeNulls;
@end

NSMutableDictionary+BVMNullReplacement.m

#import "NSMutableDictionary+BVMNullReplacement.h"

@implementation NSMutableDictionary (BVMNullReplacement)

- (void)bvm_removeNulls {
    NSArray *keysForNullValues = [self allKeysForObject:[NSNull null]];
    [self removeObjectsForKeys:keysForNullValues];

    NSArray *keys = self.allKeys;
    for (int i = 0; i < keys.count; i++) {
        id key = keys[(NSUInteger) i];
        if ([self[key] isKindOfClass:[NSMutableDictionary class]]) {
            [self[key] bvm_removeNulls];
        } else if ([self[key] isKindOfClass:[NSMutableArray class]]) {
            [self[key] bvm_removeNulls];
        }
    }
}

@end

@implementation NSMutableArray (BVMNullReplacement)

- (void)bvm_removeNulls {
    // Remove all nulls
    [self removeObjectIdenticalTo:[NSNull null]];

    // Recurse
    for (NSUInteger idx = 0; idx < [self count]; idx++) {
        id object = self[idx];
        if ([object isKindOfClass:[NSMutableDictionary class]]) {
            [((NSMutableDictionary *) object) bvm_removeNulls];
        } else if ([object isKindOfClass:[NSMutableArray class]]) {
            [((NSMutableArray *) object) bvm_removeNulls];
        }
    }
}

@end