How to remove a null value from NSDictionary

Question

I have a JSON Feed:

{
            "count1" = 2;
            "count2" = 2;
            idval = 40;
            level = "<null>";
            "logo_url" = "/assets/logos/default_logo_medium.png";
            name = "Golf Club";
            "role_in_club" = Admin;
}

The problem is the "<null>" that I cannot figure out how to remove from the NSDictionary before saving it to NSUserDefaults.

Please help me solve this issue. Thankyou!

Answer 1

I tried the solution for your question and i got it

NSDictionary *dict = [[NSDictionary alloc]initWithObjectsAndKeys:@"2",@"count1",@"2",@"count2",@"40",@"idval",@"<null>",@"level",@"/assets/logos/default_logo_medium.png",@"logo_url",@"Golf Club",@"name",@"role_in_club",@"Admin", nil];
NSMutableDictionary *mutableDict = [dict mutableCopy];
for (NSString *key in [dict allKeys]) {
    if ([dict[key] isEqual:[NSNull null]]) {
        mutableDict[key] = @""; 
    }
    if([dict[key] isEqualToString:@"<null>"])
    {
        mutableDict[key] = @"";
    }
}
dict = [mutableDict copy];
NSLog(@"The dict is - %@",dict);

Finally the answer is

The dict is - {
Admin = "role_in_club";
count1 = 2;
count2 = 2;
idval = 40;
level = "";
"logo_url" = "/assets/logos/default_logo_medium.png";
name = "Golf Club";
}

Answer 2

Another variation, without (explicit) loop:

NSMutableDictionary *dict = [yourDictionary mutableCopy];
NSArray *keysForNullValues = [dict allKeysForObject:[NSNull null]];
[dict removeObjectsForKeys:keysForNullValues];

Answer 3

I am doing in this way.

NSMutableDictionary *prunedDict = [NSMutableDictionary dictionary];
[self enumerateKeysAndObjectsUsingBlock:^(NSString *key, id obj, BOOL *stop) {
  if (![obj isKindOfClass:[NSNull class]]) {
    prunedDict[key] = obj;
  }
}];

Answer 4

I belive this is the most resource saving way

// category implementation on NSDictionary

- (NSDictionary *)dictionaryByRemovingNullValues {

    NSMutableDictionary * d;
    for (NSString * key in self) {

        if (self[key] == [NSNull null]) {
            if (d == nil) {
                d = [NSMutableDictionary dictionaryWithDictionary:self];
            }
            [d removeObjectForKey:key];
        }

    }

    if (d == nil) {
        return self;
    }

    return d;
}

Answer 5

Add this 3 methods in your view controller, and call this method like this way

NSDictionary *dictSLoginData = [self removeNull:[result valueForKey:@"data"]];

- (NSDictionary*)removeNull:(NSDictionary *)dict {

    NSMutableDictionary *replaced = [NSMutableDictionary dictionaryWithDictionary: dict];

    const id nul = [NSNull null];
    const NSString *blank = @"";

    for (NSString *key in [dict allKeys]) {

        const id object = [dict objectForKey: key];
        if (object == nul) {
            [replaced setObject: blank forKey: key];
        } else if([object isKindOfClass: [NSDictionary class]]) {
            [replaced setObject: [self replaceNull:object] forKey: key];
        } else if([object isKindOfClass: [NSArray class]]) {
            [replaced setObject: [self replaceNullArray:object] forKey: key];
        }
    }
    return [NSDictionary dictionaryWithDictionary: replaced];
}

- (NSArray *)replaceNullArray:(NSArray *)array {

    const id nul = [NSNull null];
    const NSString *blank = @"";

    NSMutableArray *replaced = [NSMutableArray arrayWithArray:array];

    for (int i=0; i < [array count]; i++) {
        const id object = [array objectAtIndex:i];
        if (object == nul) {
            [replaced replaceObjectAtIndex:i withObject:blank];
        } else if([object isKindOfClass: [NSDictionary class]]) {
            [replaced replaceObjectAtIndex:i withObject:[self replaceNull:object]];
        } else if([object isKindOfClass: [NSArray class]]) {
            [replaced replaceObjectAtIndex:i withObject:[self replaceNullArray:object]];
        }
    }
    return replaced;
}

- (NSDictionary *)replaceNull:(NSDictionary *)dict {

    const id nul = [NSNull null];
    const NSString *blank = @"";

    NSMutableDictionary *replaced = [NSMutableDictionary dictionaryWithDictionary: dict];

    for (NSString *key in [dict allKeys]) {
        const id object = [dict objectForKey: key];
        if (object == nul) {
            [replaced setObject: blank forKey: key];
        } else if ([object isKindOfClass: [NSDictionary class]]) {
            [replaced setObject: [self replaceNull:object] forKey: key];
        } else if([object isKindOfClass: [NSArray class]]) {
            [replaced setObject: [self replaceNullArray:object] forKey: key];
        }
    }
    return replaced;
}

Answer 6

Iterate through the dictionary and look for any null entries and remove them.

NSMutableDictionary *prunedDictionary = [NSMutableDictionary dictionary];
for (NSString * key in [yourDictionary allKeys])
{
    if (![[yourDictionary objectForKey:key] isKindOfClass:[NSNull class]])
        [prunedDictionary setObject:[yourDictionary objectForKey:key] forKey:key];
}

After that, prunedDictionary should have all non-null items in the original dictionary.