01_refresh_token_provider_class.dart

// Definition
@Riverpod(keepAlive: true)
_RefreshToken refreshToken(RefreshTokenRef ref) => _RefreshToken(ref);

class _RefreshToken {
  const _RefreshToken(this.ref);

  final Ref ref;

  Future<RefreshTokenResponse> call({
    required RefreshTokenBody body,
  }) async {
    final client = ref.watch(restClientProvider);
    final response = await client.refreshToken(body);
    return response.data;
  }
}

/// call
Future<void> callToSingleProvider() async {
  final container = ProviderContainer();
  const body = RefreshTokenBody(userId: 'USER_001');
  final response = await container.read(refreshTokenProvider)(body: body);
  print(response);
}

02_refresh_token_provider_function.dart

// Definition

@Riverpod(keepAlive: true)
Future<RefreshTokenResponse> Function({
  required RefreshTokenBody body,
}) refreshToken(
  RefreshTokenRef ref,
) =>
    ({required body}) async {
      final client = ref.watch(restClientProvider);
      final response = await client.refreshToken(body);
      return response.data;
    };

/// call
Future<void> callToSingleProvider() async {
  final container = ProviderContainer();
  const body = RefreshTokenBody(userId: 'USER_001');
  final response = await container.read(refreshTokenProvider)(body: body);
  print(response);
}

03_some_feature_or_widget.dart

/// call
Future<void> callDirectRestClient() async {
  final container = ProviderContainer();
  const body = RefreshTokenBody(userId: 'USER_001');
  final response =
      await container.read(favomatchRestClientProvider).refreshToken(body);
  print(response);
}