Using Ember component's methods inside template

I've just started learning Ember and one thing I'm confused that if I can access component's method inside the template.

For example, I have a note-list component that render list of note-line as follow:

<ul class="list">
  {{#each notes as |note|}}
    {{note-line note=note index=@index selected=(isSelected note)}}
  {{/each}}
</ul>

The note-list component is defined as:

Ember.Component.extend({
    tagName: '',
    isSelected(note) {
        return note.id === this.get('selectedNote').id
    }
})

But I'm getting error Assertion Failed: A helper named 'isSelected' could not be found.

I think I could solve it with helpers, but it seems to be not a good solution to create a separate helper for a behaviour of a specific component.

Please help to advise me some better way to deal with it.

Thanks very much.