Modal Service

components.modal-owner.js

import Ember from 'ember';

export default Ember.Component.extend({
  modal: Ember.inject.service(),
  
  actions: {
    close() {
      this.get('modal').close(); 
    }
  }
});

components.my-modal.js

import Ember from 'ember';

export default Ember.Component.extend({
  modal: Ember.inject.service(),
  
  actions: {
    next() {
      this.get('modal').open('my-other-modal');
    },
    close() {
      this.close(); 
    }
  }
});

components.my-other-modal.js

import Ember from 'ember';

export default Ember.Component.extend({
  actions: {
    close() {
      this.close(); 
    }
  }
});

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  modal: Ember.inject.service(),
  appName: 'Ember Twiddle',
  actions: {
    openModal() {
      this.get('modal').open('my-modal');
    }
  }
});

services.modal.js

import Ember from 'ember';

export default Ember.Service.extend({
  componentName: null,
  
  open(name) {
    this.set('componentName', name); 
  },
  
  close() {
    this.set('componentName', null); 
  }
});

styles.app.css

body {
  margin: 12px 16px;
  font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif;
  font-size: 12pt;
}

.modal-scrim {
  position: fixed;
  top: 0;
  bottom: 0;
  left: 0;
  right: 0;
  background-color: rgba(0, 0, 0, 0.3);
  display: flex;
	justify-content: center;
  align-items: center;
}

.modal-body {
  background: #fff;
  padding: 20px;
}

templates.application.hbs

<h1>Welcome to {{appName}}</h1>
<br>
<br>
<button {{action "openModal"}}>Open Modal</button>
{{outlet}}
<br>
<br>
{{modal-owner}}

templates.components.modal-owner.hbs

{{#if modal.componentName}}
	<div class="modal-scrim">
  	<div class="modal-body">
    	{{component modal.componentName close=(action "close")}}
    </div>
  </div>
{{/if}}

templates.components.my-modal.hbs

modal content

<button {{action "next"}}>Next</button>
<button {{action "close"}}>Close</button>

templates.components.my-other-modal.hbs

more modal content

<button {{action "close"}}>Close</button>

twiddle.json

{
  "version": "0.10.1",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "2.6.0",
    "ember-data": "2.6.1",
    "ember-template-compiler": "2.6.0"
  },
  "addons": {}
}