action issue

components.my-component.js

import Ember from 'ember';

export default Ember.Component.extend({
  message: Ember.computed('computeMessage', function() {
    return this.get('computeMessage')();
  }),
  
  actions: {
    trigger() {
      alert(this.get('computeMessage')());
      alert(this.get('message'));
    }
  }
});

controllers.application.js

import Ember from 'ember';
const { computed } = Ember;

export default Ember.Controller.extend({
  computeMessage: computed(() => (greeting) => 'none'),
  
  actions: {
    updateComputation(name) {
      this.set('computeMessage', (greeting) => `${greeting}, ${name}`);
    }
  }
});

templates.application.hbs

<button onclick={{action 'updateComputation' 'a'}}>A</button>
<button onclick={{action 'updateComputation' 'b'}}>B</button>

{{my-component computeMessage=(action computeMessage 'Hello')}}

templates.components.my-component.hbs

<button onclick={{action 'trigger'}}>Trigger</button>

twiddle.json

{
  "version": "0.10.7",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "2.10.1",
    "ember-data": "2.10.0",
    "ember-template-compiler": "2.10.1",
    "ember-testing": "2.9.1"
  },
  "addons": {}
}