Replace null (NSNull) with empty string in object

gistfile1.md

If you are dealing with an unstable API, you may want to iterate through all the keys to check for null. This will prevent crash when saving the object as well.

+ (id)replaceNullWithEmptyStringForObject:(id)object {
    if ([object isKindOfClass:[NSArray class]]) {
        NSMutableArray *mutableArray = [object mutableCopy];
        [mutableArray enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
            [mutableArray setObject:[self replaceNullWithEmptyStringForObject:obj] atIndexedSubscript:idx];
        }];
        
        return mutableArray;
    } else {
        NSMutableDictionary *mutableDictionary = [object mutableCopy];
        [mutableDictionary enumerateKeysAndObjectsUsingBlock:^(id key, id value, BOOL *stop) {
            if ([value isKindOfClass: [NSMutableDictionary class]]) {
                [self replaceNullWithEmptyStringForObject:value];
            } else if ([value isKindOfClass:[NSArray class]]) {
                [mutableDictionary setObject:[self replaceNullWithEmptyStringForObject:value] forKey:key];
            } else if ([value isKindOfClass:[NSNull class]]) {
                [mutableDictionary setValue:@"" forKey:key];
            }
        }];
        
        return mutableDictionary;
    }
}

Tested:

#import "NSObject+Utils.h"

@implementation NSObject (Utils)

- (id)eliminatedNull {
    if ([self isKindOfClass:[NSArray class]]) {
        NSMutableArray *mutableArray = [NSMutableArray new];
        [self.mutableCopy enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
            [mutableArray setObject:[obj eliminatedNull] atIndexedSubscript:idx];
        }];

        return mutableArray;
    } else if ([self isKindOfClass:[NSDictionary class]]) {
        NSMutableDictionary *mutableDictionary = [NSMutableDictionary new];
        [self.mutableCopy enumerateKeysAndObjectsUsingBlock:^(id key, id value, BOOL *stop) {
            [mutableDictionary setObject:[value eliminatedNull] forKey:key];
        }];

        return mutableDictionary;
    } else {
        id result;
        if ([self isKindOfClass:[NSNull class]]) {
            result = @"";
        } else {
            result = self;
        }
        return result;
    }
}
@end