Why angular uses url segment?

A UrlSegment is a part of a URL between the two slashes. It contains a path and the matrix parameters associated with the segment.

Matrix parameters are tied to a path segment, while query parameters are tied to the URL. They have different semantics.

Consider:

localhost:3000/heroes;id=15;foo=foo/bar/baz
// instead of localhost:3000/heroes/bar/baz?id=15&foo=foo

The parameters are tied to heroes no to the URL. When you access the route.url, you will see this

this.route.url.subscribe((url: UrlSegment[]) => {
  let heroes = url[0];
  let heroesMatrix = heroes.parameters();
  // heroes should contain id=15, foo=foo
  let bar = url[1].path; // 15
  let baz = url[2].path; //foo
})

For matrix parameters you can also subscribe to params instead of peeling them out of url.

this.paramSubscription = this.activeRoute.params.subscribe(params => {
  const bar = params['bar'];
  const baz = params['baz'];
});

With an Angular app, the only people who really care about these parameters are us the developer. The user doesn’t care. It is not a REST API where we should stick to well known semantics. For out Angular app, as long as we the developer know how to use params (whether matrix or query), it shouldn’t matter which one we use.