Make the URL carry the right state

Paths identify resources

For /books/:bookId, the actual URI /books/42 supplies bookId = 42. Receiving a string does not establish that a record exists. Validate the identifier and handle a missing or inaccessible resource in your application.

Queries refine a destination

A URI such as /books?sort=recent&page=2 can represent a list with shareable filters. Parse numbers safely and choose explicit defaults when values are absent or malformed. URI constructors handle encoding more reliably than manual string concatenation.

Keep extra optional

extra can carry an object during navigation, but someone who opens a copied URL may not have that object. The router supports an extra codec for serialization requirements; that still calls for a deliberate design and does not justify putting secrets in browser history.

Choose one source of truth

If both the URL and a controller own the same filter, specify which one wins on Back, Forward, and reload. Rebuild from the URI when a link changes the destination. Never place passwords, tokens, or sensitive personal information in path or query parameters.

final bookId = state.pathParameters['bookId'];
final sort = state.uri.queryParameters['sort'] ?? 'title';
final page = int.tryParse(
  state.uri.queryParameters['page'] ?? '',
) ?? 1;

final destination = Uri(
  path: '/books',
  queryParameters: {'sort': 'recent', 'page': '2'},
);
context.go(destination.toString());