How can I add null values in JSONC?

Question

I am using JSONC library in c to create json. But I can't create null values. How can I create the following json data using JSONC library? {"status" : null }

Answer 1

According to the interface of json-c library, I think you can delete the nameval pair first from the object, and then add a field with NULL as val:

json_object_object_del(jexample, "status");
json_object_object_add(jexample, "status", NULL);

Reference: https://github.com/json-c/json-c/blob/master/json_object.h

See API definition:

/*
 * @param obj the json_object instance
 * @param key the object field name (a private copy will be duplicated)
 * @param val a json_object or NULL member to associate with the given field
 *
 * @return On success, <code>0</code> is returned.
 *  On error, a negative value is returned.
 */
    JSON_EXPORT int json_object_object_add(struct json_object* obj, const char *key,
                       struct json_object *val);

Answer 2

The library has a method to set a null value. https://github.com/json-c/json-c/blob/master/json_object.h#L1000

You can add the value as

json_object_object_add(json_object, "nullable_field", json_object_new_null());

As result, you will have:

{
    ...
    "nullable_field":null,
    ...
}