Route parameters

Declare, read, and validate route parameters in Aurelia's router, including required, optional, wildcard, and constrained segments.

Route parameters let you map dynamic pieces of a URL to runtime data. This guide covers how to declare each parameter style, consume values inside components, and coordinate parent/child segments.

1. Declare parameterized paths

Use the path field inside @route (or route configs) to describe parameters.

Syntax	Meaning	Example
:id	Required segment	/users/42
:id?	Optional segment	/users and /users/42
*rest	Wildcard remainder	/files/src/app/main.ts
:id{{^\\d+$}}	Constrained segment (regex)	/orders/1001 (numbers only)

import { route } from '@aurelia/router';

@route({
  routes: [
    { path: 'users/:id', component: UserDetail },
    { path: 'users/:id/edit', component: UserEditor },
    { path: 'files/*path', component: FileViewer },
  ]
})
export class AdminLayout {}

Destructure params inside lifecycle hooks

Each lifecycle hook receives a Params object. The router always supplies a string value (or undefined if optional and missing), so add your own parsing as needed.

import { IRouteViewModel, Params } from '@aurelia/router';

export class UserDetail implements IRouteViewModel {
  userId = '';

  canLoad(params: Params) {
    this.userId = params.id ?? '';
    return !!this.userId;
  }
}

For asynchronous preparation, use loading and throw or return false to fail the navigation if something looks wrong.

2. Access parent and child parameters together

Nested routes often need both parent and child IDs (for example /companies/10/projects/17). Resolve IRouteContext and use getRouteParameters to aggregate values.

import { IRouteContext } from '@aurelia/router';
import { resolve } from '@aurelia/kernel';

export class ProjectDetail {
  private readonly routeContext = resolve(IRouteContext);

  get identifiers() {
    return this.routeContext.getRouteParameters({
      mergeStrategy: 'parent-first',
    });
  }
}

Callers can opt in to query parameters too:

this.routeContext.getRouteParameters({ includeQueryParams: true });

3. Work with query parameters alongside path params

Even though query parameters are not part of the path definition, you can treat them as a cohesive set.

import { IRouter, ICurrentRoute } from '@aurelia/router';
import { resolve } from '@aurelia/kernel';

export class FilterPanel {
  private readonly router = resolve(IRouter);
  private readonly current = resolve(ICurrentRoute);

  apply(filters: Record<string, string>) {
    return this.router.load(this.current.path, {
      queryParams: filters,
    });
  }
}

Use ICurrentRoute to observe query changes reactively (see Router state management).

4. Generate links with parameters

The load attribute on <a> elements handles interpolation for you. Bind params to an object so that the router formats the URL consistently.

<a load="route: users/:id; params.bind: { id: user.id }">Open profile</a>
<a load="route: companies/:companyId/projects/:projectId; params.bind: { companyId, projectId }"></a>

When generating programmatic instructions, pass params alongside the component:

router.load({ component: ProjectDetail, params: { companyId: '10', projectId: '17' } });

5. Validate and coerce parameters

Guard logic belongs in the canLoad hook. You can redirect by returning a string instruction or a ViewportInstruction.

import { IRouteViewModel, Params } from '@aurelia/router';

export class ReportLoader implements IRouteViewModel {
  canLoad(params: Params) {
    const date = params.date;
    if (!date || Number.isNaN(Date.parse(date))) {
      return 'reports/today';
    }

    return true;
  }
}

For stricter validation, pair regex-constrained paths with canLoad type checks so users get feedback before hitting your backend.

6. Test parameterized routes

Unit tests can render a component, navigate to a parameterized path, and assert how parameters flow through the lifecycle.

const fixture = await createFixture(UserDetail).startApp();
await fixture.router.load('users/10');
expect(fixture.root.controller.viewModel.userId).toBe('10');

You can also mock IRouteContext or ICurrentRoute to simulate specific parameter sets without spinning up the full router.

Outcome recipes

Bookmarkable search filters

Goal: encode search term, page number, and filter chips in the URL so users can share the view.

1. Define the base route /search and keep filters in the query string (?q=aurelia&page=2&tag=forms).

2. Use ICurrentRoute.query to read the current filters in attached() and hydrate your form.

3. When filters change, call router.load(this.current.path, { queryParams: newFilters }) to update the URL without reloading the whole app.

Checklist:

• Refreshing /search?q=router&page=3 shows the same filter state.

• router.load uses historyStrategy: 'replace' when only filters change to avoid polluting history (configure via navigation options if needed).

Parent + child identifiers

Goal: address /companies/:companyId/projects/:projectId and display both IDs in deeply nested children.

1. Parent route declares companies/:companyId and renders a <au-viewport> for projects.

2. Child route declares projects/:projectId.

3. Inside any descendant component call routeContext.getRouteParameters({ mergeStrategy: 'parent-first' }) to get both IDs.

Checklist:

• Navigating between different projects preserves the company context.

• routeContext.getRouteParameters() returns { companyId: '10', projectId: '17' } at every depth.

Redirect invalid params

Goal: keep /reports/:date constrained to valid ISO dates.

1. Constrain the route with :date{{^\\d{4}-\\d{2}-\\d{2}$}} to block obviously bad paths.

2. Inside canLoad, parse the date and return 'reports/today' if invalid.

3. Emit a toast notification through a shared service to explain the redirect.

Checklist:

• /reports/2024-13-01 never renders the detail view; users land on /reports/today.

• Valid dates continue to the report screen.

Related resources

• Configuring routes

• Routing lifecycle

• Navigating

• Child routing playbook