bool

       MongoDB, Inc

       2009-present, MongoDB, Inc.

1.30.4                                            Jun 08, 2025         MONGOC_FIND_AND_MODIFY_OPTS_SET_FIELDS(3)

       Adds fields argument to the builder.

       fields does not have to remain valid after calling this function.

       • opts: A mongoc_find_and_modify_opts_t.

       • fields:  A  subset  of fields to return. Choose which fields to include by appending {fieldname:1} for
         each fieldname, or excluding it with {fieldname:0}.

       Returns true if it successfully added the option to the builder, otherwise false.

       fields.c

          void
          fam_fields (mongoc_collection_t *collection)
          {
             mongoc_find_and_modify_opts_t *opts;
             bson_t fields = BSON_INITIALIZER;
             bson_t *update;
             bson_t reply;
             bson_error_t error;
             bson_t query = BSON_INITIALIZER;
             bool success;

             /* Find Zlatan Ibrahimovic */
             BSON_APPEND_UTF8 (&query, "lastname", "Ibrahimovic");
             BSON_APPEND_UTF8 (&query, "firstname", "Zlatan");

             /* Return his goal tally */
             BSON_APPEND_INT32 (&fields, "goals", 1);

             /* Bump his goal tally */
             update = BCON_NEW ("$inc", "{", "goals", BCON_INT32 (1), "}");

             opts = mongoc_find_and_modify_opts_new ();
             mongoc_find_and_modify_opts_set_update (opts, update);
             mongoc_find_and_modify_opts_set_fields (opts, &fields);
             /* Return the new tally */
             mongoc_find_and_modify_opts_set_flags (opts, MONGOC_FIND_AND_MODIFY_RETURN_NEW);

             success = mongoc_collection_find_and_modify_with_opts (collection, &query, opts, &reply, &error);

             if (success) {
                char *str;

                str = bson_as_canonical_extended_json (&reply, NULL);
                printf ("%s\n", str);
                bson_free (str);
             } else {
                fprintf (stderr, "Got error: \"%s\" on line %d\n", error.message, (int) (__LINE__));
             }

             bson_destroy (&reply);
             bson_destroy (update);
             bson_destroy (&fields);
             bson_destroy (&query);
             mongoc_find_and_modify_opts_destroy (opts);
          }

       Outputs:

          {
             "lastErrorObject"
                : {"updatedExisting" : true, "n" : 1},
                  "value"
                  : {"_id" : {"$oid" : "56562a99d13e6d86239c7b00"}, "goals" : 343},
                    "ok" : 1
          }

          bool
          mongoc_find_and_modify_opts_set_fields (mongoc_find_and_modify_opts_t *opts,
                                                  const bson_t *fields);