Access model-attribute in ArrayController

I'd like to add a computed property to a controller containing an attribute from the model. I've got a list of blog-posts belonging to the same category. I added a component rendering breadcrumbs via setting a breadcrumb property in the controller.

Up until now I rendered the category-name in the template via {{ this.firstObject.category.name }}

This doesn't work in the controller. How can I get the model's attributes?

Here's my route and controller so far:

routes/category.js

import Ember from 'ember';

export default Ember.Route.extend({
  model: function(params) {
    return this.store.find('post', { category: params.category });
  }
});

controllers/category.js

import Ember from 'ember';

export default Ember.ArrayController.extend({
  breadCrumb: function() {
    var posts = this.get('post'); // <-- is empty
    console.log(this.firstObject.category.name);
    return posts.get(this.firstObject.category.name); // <-- doesn't work
  }
});