Json-glib: how can i get the jsonobject of the current node in jsonreader?

Platform
1

as the object

i think it’s a stupid question, but i cannot find the way

i tried with json_reader_get_value but it returns an error “The current position holds a “jsonobject” and not a value”

2

You don’t access JsonObject and JsonArray directly with JsonReader; instead, you’re supposed to “enter” an object, and then leave it.

For instance, given something like:

[
    { "foo": "bar", "baz": true },
    { "foo": "hello", "baz": false }
]

Your reader instance can be used like this:

// Assert that the element is an array
g_assert_true (json_reader_is_array (reader));

// Read the first element of the array
json_reader_read_element (reader, 0);

// Assert that the element contains an object
g_assert_true (json_reader_is_object (reader));

// Enter the "foo" member of the object
json_reader_read_member (reader, "foo")
foo[0] = json_reader_get_string_value (reader);
json_reader_end_member (reader);

// Enter the "bar" member of the object
json_reader_read_member (reader, "bar");
bar[0] = json_reader_get_boolean_value (reader);
json_reader_end_member (reader);

// Leave the first element of the array
json_reader_end_element (reader);

// Enter the second element
json_reader_read_element (reader, 1);

// Repeat…

The JsonReader object is used to consume the object model while traversing it; if you want to access the actual data types, then you should use the JsonNode API.

1 Like
3

sorry i forgot to provide the json

{
    "object_a": {"id": 4, "name": "foo" },
    "object_b": {"color": "red", "model":"supreme"}
}

and the code

json_reader_read_element (reader, 0);
json_reader_get_member_name (reader); // ok it returns "object_a"
json_reader_is_object (reader); // ok it returns true
json_reader_get_value (reader); // error: The current position holds a “jsonobject” and not a value

so i cannot get object_a.id (or name)

4

Yes, you’re trying to get the JsonObject, which is not possible with JsonReader. You’re supposed to enter the nested object and retrieve its members, e.g.

json_reader_read_member (reader, "object_a");

json_reader_read_member (reader, "id");
gint64 id = json_reader_get_int_value (reader); // id = 4
json_reader_end_member (reader); // leaves "id"

json_reader_read_member (reader, "name");
const char *name = json_reader_get_string_value (reader); // name = "foo"
json_reader_end_member (reader); // leaves "name"

json_reader_end_member (reader); // leaves "object_a"

json_reader_read_member (reader, "object_b");
// read members of "object_b"
json_reader_end_member (reader); // leaves "object_b"
1 Like
5

ok, clear, thank you

6

This topic was automatically closed 14 days after the last reply. New replies are no longer allowed.