linux下如何提取bson中的MongoDB唯一标识_id

已经通过mongoc_collection_find()和mongoc_cursor_next()拿到想要的bson_t 类型对象现在想提取该对象中包含的MongoDB唯一标识_id。

自己找了一个笨方法实现了。

转成json，然后用_id做key来访问对应的数据

 while (mongoc_cursor_more (cursor) && mongoc_cursor_next (cursor, &doc)) {
      str = bson_as_json (doc, NULL);
      printf ("%s\n", str);
      bson_free (str);
   }

 bson_t query;
bson_t child;
bson_init(&query);

BSON_APPEND_INT64(&query, "id", 0);

mongoc_cursor_t m_pCursor = mongoc_collection_find(m_pCollection,
    MONGOC_QUERY_NONE,
    0,
    0,
    0,
    &query,
    NULL,  /* Fields, NULL for all. */
    NULL); /* Read Prefs, NULL for default */

bson_destroy(&query);
bson_error_t error;
if (mongoc_cursor_error(m_pCursor, &error)) {
    cout << "Query Failure: " << error.message;
    return;
}

const bson_t *doc;

while (!mongoc_cursor_error(m_pCursor, &error)
    && mongoc_cursor_more(m_pCursor))
{
    if (mongoc_cursor_next(m_pCursor, &doc))
    {
        GetRecord(doc);
    }
    else
    {
        break;
    }
}
if (mongoc_cursor_error(m_pCursor, &error)) {
    cout << "Query Failure: " << error.message;
}

mongoc_cursor_destroy(m_pCursor);