Defining default values

Reading parameter values

For any or all parameters defined during setup, it is possible to specify a default value.

If the parameter is not included in the URL, ngx-url-state will automatically add the query parameter with the specified default value:

• at initialisation (when listen is called)
• whenever a change to the activated route is detected.

This provides a convenient way to guarantee that certain values exist.

Defining a default value for a parameter

this.urlState = this.urlStateService.listen<ProductsPageParams>({
  ...
  paramDefinitions: {
    page: {
      mapper: IntMapper,
      defaultValue: 1
    },

Automatic redirection

Any parameters with a defaultValue are deemed to be required parameters. Whenever ngx-url-state detects that a required parameter is missing in the URL, it will automatically perform a redirect to add that parameter with the specified default value.

note

Automatic redirects to insert required parameters use the ReplaceHistory navigation mode, to avoid breaking the history stack.

Example:

1. User starts on /home and follows a link in the navbar to /products
2. ngx-url-state automatically redirects to /products?page=1 because page has a defaultValue configured
3. User navigates back (browser back button), and they land on /home, not /products.