Router

A router is a core component of H4. It's used to route requests to the appropriate handler.

Creating a router

Create a router instance with optional base path:

// Default router with no base path
final router = createRouter();
 
// Router with base path
final apiRouter = createRouter(basePath: '/api');

You can create multiple routers with different base paths and combine them:

void main() {
  final app = createApp();
  final v1Router = createRouter(basePath: '/v1');
  final v2Router = createRouter(basePath: '/v2');
 
  app.use(v1Router);
  app.use(v2Router);
 
  v1Router.get("/users", (event) => getUserList());
  v2Router.get("/users", (event) => getUserListV2());
}

This allows you to organize routes better in some cases. E.g adding versioning to your app with routes prefixed with v1, v2, etc.

Route Methods

Handle all HTTP methods with explicit handlers:

router.get("/resource", (event) => "GET handler");
router.post("/resource", (event) => "POST handler");
router.put("/resource", (event) => "PUT handler");
router.delete("/resource", (event) => "DELETE handler");
router.patch("/resource", (event) => "PATCH handler");
router.head("/resource", (event) => "HEAD handler");
router.options("/resource", (event) => "OPTIONS handler");
router.trace("/resource", (event) => "TRACE handler");
router.all("/resource", (event) => "Handles ALL method types");

Path Parameters

Capture dynamic path segments using colon syntax:

router.get("/users/:id", (event) {
  final userId = getRouteParam(event, 'id');
  return {'user': fetchUser(userId)};
});
 
router.get("/posts/:slug/comments/:commentId", (event) {
  final slug = getRouteParam(event, 'slug');
  final commentId = getRouteParam(event, 'commentId');
  return fetchComment(slug, commentId);
});

Catch-All Routes

Handle unmatched routes with wildcard pattern:

// Match all requests under /api
router.all("/api/*", handle404);
 
// Global 404 handler example
router.all("**", (event) {
  event.statusCode = 404;
  return "Route not found";
});

Response Handling

Return various response types directly:

router.get("/text", (event) => "Plain text response");
router.get("/json", (event) => {"key": "value"});
router.get("/html", (event) => "<h1>Hello</h1>");
router.get("/bytes", (event) => [1, 2, 3]);