Delete NSNull object in Json object

convertNullObject

/**
 *  把response中的NSNull对象删除掉
 *
 *  @param response 要处理的对象
 *
 *  @return 删除掉NSNull后的新对象
 */
- (id)convertNullObject:(id)response
{
    if (response == nil || [response isKindOfClass:[NSNull class]]) {
        return nil;
    }
    
    if ([response isKindOfClass:[NSArray class]]) {
        NSMutableArray *tempResponse = [NSMutableArray array];
        for (id item in response) {
            id newItem = [self convertNullObject:item];
            if (newItem) {
                [tempResponse addObject:newItem];
            }
        }
        
        if (tempResponse.count > 0) {
            return tempResponse;
        } else {
            return nil;
        }
    } else if ([response isKindOfClass:[NSDictionary class]]) {
        NSMutableDictionary *tempResponse = [NSMutableDictionary dictionary];
        for (id key in [response allKeys]) {
            id value = [response objectForKey:key];
            id newValue = [self convertNullObject:value];
            if (!newValue) {
                continue;
            }
            
            [tempResponse setObject:newValue forKey:key];
        }
        
        if (tempResponse.count > 0) {
            return tempResponse;
        } else {
            return nil;
        }
    } else {
        return response;
    }
}