New Twiddle

components.my-componenta.js

import Ember from 'ember';

export default Ember.Component.extend({
  actions: {
    open(){
      //do stuff
      let image = 'yay image'
      this.get('childManager').select(image)
    }
  }
});

components.my-componentb.js

import Ember from 'ember';

export default Ember.Component.extend({
  init(){
    this._super(...arguments);
    this.get('registerComponentManager')({
      select: (image) => this.send('select', image)
    })
  },
  actions: {
    select(image){
      this.set('image', image)
    }
  }
});

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName: 'Ember Twiddle'
});

templates.application.hbs

<h1>Welcome to {{appName}}</h1>
<br>
<br>
{{#my-componenta as |child|}}
	{{#child as |select|}}
  {{/child}}
{{/my-componenta}}
<br>
<br>

templates.components.my-componenta.hbs

{{yield (component "my-componentb"
  registerComponentManager=(action (mut childManager))
)}}

templates.components.my-componentb.hbs

{{yield (action 'select')}}
{{#if image}}
	{{image}}
{{else}}
	no image
{{/if}}

twiddle.json

{
  "version": "0.15.0",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.js",
    "ember": "3.2.2",
    "ember-template-compiler": "3.2.2",
    "ember-testing": "3.2.2"
  },
  "addons": {
    "ember-data": "3.2.0"
  }
}