Conditional binding for a computed property

controllers.application.js

import Ember from 'ember';

let _myComputedProperty = Ember.computed('foobar', function() {
  let foobar = this.get('foobar');
  console.log('myComputedProperty triggered >', foobar);
  return '_' + foobar + '_';
});
  
export default Ember.Controller.extend({
  
  // Using a flag results in the correct UI result, but the
  // computed is still trying to recalculate its value
  // every single time
  
  /*
  turnOff: false,
  
  myComputedProperty: Ember.computed('foobar', 'turnOff', function() {

    console.log('myComputedProperty triggered');
    
    if (this.get('turnOff')) {
      return this.get('myComputedProperty');
    }
    
	  let foobar = this.get('foobar');
    return '_' + foobar + '_';
  }),
  */
  
  foobar: 0,
  
  myComputedProperty: _myComputedProperty, 
  
  actions: {
  
    startUpdates: function() {
      setInterval(() => {
        this.incrementProperty('foobar');
      }, 700);
    },
    
    turnOffComputed: function() {
      //this.set('turnOff', true);
      
      // lock it to the last known value
      let myComputedProperty = this.get('myComputedProperty');
      this.set('myComputedProperty', myComputedProperty);
    },
    
    turnOnComputed: function() {
      this.set('myComputedProperty', _myComputedProperty);
    }
  }
  
});

templates.application.hbs

<h1>Conditional Binding</h1>
<br>
<br>

<button {{action "startUpdates"}}>start infinite computed updates</button>
<br>
<br>

<button {{action "turnOffComputed"}}>turn off computed</button>
<button {{action "turnOnComputed"}}>turn on computed</button>

<br>
<br>

foobar: {{foobar}}
<br>
myComputedProperty: {{myComputedProperty}}

{{outlet}}
<br>
<br>

twiddle.json

{
  "version": "0.10.4",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "2.7.0",
    "ember-data": "2.7.0",
    "ember-template-compiler": "2.7.0"
  },
  "addons": {}
}