JsonReader

json.reader.Reader provides a simple, cursor-based API for parsing a JSON DOM.

It is similar, in spirit, to the XML Reader API.

Using json.reader.Reader

g_autoptr(JsonParser) parser = json_parser_new ();

// str is defined elsewhere
json_parser_load_from_data (parser, str, -1, NULL);

g_autoptr(JsonReader) reader = json_reader_new (json_parser_get_root (parser));

json_reader_read_member (reader, "url");
  const char *url = json_reader_get_string_value (reader);
  json_reader_end_member (reader);

json_reader_read_member (reader, "size");
  json_reader_read_element (reader, 0);
    int width = json_reader_get_int_value (reader);
    json_reader_end_element (reader);
  json_reader_read_element (reader, 1);
    int height = json_reader_get_int_value (reader);
    json_reader_end_element (reader);
  json_reader_end_member (reader);

Error handling

In case of error, json.reader.Reader will be set in an error state; all subsequent calls will simply be ignored until a function that resets the error state is called, e.g.:

// ask for the 7th element; if the element does not exist, the
// reader will be put in an error state
json_reader_read_element (reader, 6);

// in case of error, this will return NULL, otherwise it will
// return the value of the element
str = json_reader_get_string_value (value);

// this function resets the error state if any was set
json_reader_end_element (reader);

If you want to detect the error state as soon as possible, you can use json.reader.Reader.getError:

// like the example above, but in this case we print out the
// error immediately
if (!json_reader_read_element (reader, 6))
  {
    const GError *error = json_reader_get_error (reader);
    g_print ("Unable to read the element: %s", error->message);
  }