http://stackoverflow.com/questions/42918195/ember-2-handle-two-or-more-properties-in-just-one-computed-property-how-to-fil/42918765

components.my-posts.js

import Ember from 'ember';

export default Ember.Component.extend({
  
  searchPosts: Ember.computed('posts.@each.name', 'search', function() {
  var posts = this.get('posts');
  var search = this.get('search');
  return posts.filter(post => post.name.includes(search));
}),
categoryPosts: Ember.computed('posts.[]','category', function(){ 
  return this.get('posts').filter(post => post.categoryId === this.get('category'));
}),

postsFiltered: Ember.computed('searchPosts', 'categoryPosts.[]', 'search', function() {
  
  if (this.get('search')) {
    return this.get('searchPosts');
  } else {
    return this.get('categoryPosts');
  }
}),
 /* 
  postsFiltered: Ember.computed('category', 'search', function () {
    
    var posts = this.get('posts');
    var search = this.get('search');
    
    console.log('computed postsFiltered() with category: ' + this.get('category') + ', search: ' + search);
    return posts.filter((item) => item['categoryId'] === this.get('category'));
    
    // or this when I search, but I don't know how to do:
    // return posts.filter((item) => item['name'].includes(search))
  }) */
});

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName: 'Ember Twiddle',
  
  category: null,
  search:'',
  
  categories: [{name: 'Category 1', id: 1}, {name: 'Category 2', id: 2}, {name: 'Category 3', id: 3}],
  
  posts: [{name: 'Post 1', categoryId: 1}, {name: 'Post 2', categoryId: 2}, {name: 'Post 3', categoryId: 2}, {name: 'Post 4', categoryId: 3}],
  
  actions: {
  
    clickCategory(categoryId) {
      this.set('category', categoryId);
      this.set('search','');
    }
    
  }
});

templates.application.hbs

<br>
{{outlet}}

{{#each categories key="id" as |category|}}
	<button type="button" {{action 'clickCategory' category.id}}>{{category.name}}</button>
{{/each}}

{{my-posts posts=posts category=category search=search}}


<br>
<br>

templates.components.my-posts.hbs

{{yield}}
<br><br>
Search: {{input value=search}}
<br><br>
Category: {{category}}
<br><br>
{{#each postsFiltered as |post|}}
{{post.name}}<br>
{{/each}}

twiddle.json

{
  "version": "0.11.1",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "2.11.0",
    "ember-data": "2.11.0",
    "ember-template-compiler": "2.11.0",
    "ember-testing": "2.11.0"
  },
  "addons": {}
}