How can I hang the "active" class only on the current route?

I have such routes:

this.route('posts', function() {
  this.route('index', { path: '/' })
  this.route('show', { path: '/:post_path' }, function() {
    this.route('people', { path: '/people' })

    this.route('files', function() {
      this.route('images', { path: '/images' })
      this.route('videos', { path: '/videos' })
    })
  })
}),

I have a problem with the class "active".

Take, for example, this link:

http://localhost:4200/posts/1-best-post/files/images

In this case, the class "active" will hang on two links - on posts.show.files.images and on posts.show.

How to make the class "active" only for posts.show.files.images?