New Twiddle

components.quiz-multiple-choice.js

import Ember from 'ember';

export default Ember.Component.extend({
  actions: {
    updateAnswer(newValue){
      if(!this.answer){
        this.set('answer', {text: newValue})
      }else{
    		this.set('answer.text', newValue)
  		}
    }
    
  }
});

components.quiz-question.js

import Ember from 'ember';

export default Ember.Component.extend({
  showSolution: false,
  actions: {
    save(answer){
      this.saveAnswer(answer) //await this
      this.fetchSolution(this.question) //await this
      this.toggleProperty("showSolution")
    }
  }
});

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  init(){
    const quiz = {}
    const questions = [
      {name: "test1", type:"multiple-choice", quiz},
      {name: "test2", type:"multiple-choice", quiz}
    ]
    quiz.questions = questions
    this.setProperties({ quiz })
  },
  actions:{
    saveAnswer(answer){
      console.log('save answer', answer)
    },
   	fetchSolution(question){
      console.log('fetch solution')
      question.solution="solution text"
    },
    verifyTest(){
      console.log('save all answers')
      console.log('fetch all solutions')
      this.quiz.questions.forEach(q => q.solution = "solution test")
      this.toggleProperty('showSolution')
    }
  }
});

templates.application.hbs

{{#each quiz.questions as |question|}}
	<QuizQuestion
  	@question={{question}}
    @saveAnswer={{action "saveAnswer"}} 
    @fetchSolution={{action "fetchSolution"}}
    @showSolution={{showSolution}}
  />
{{/each}}
Test : {{input type="checkbox" checked=quiz.test}}
{{#if quiz.test}}
	<button {{action "verifyTest" answer}} >verify</button>
{{/if}}

templates.components.quiz-multiple-choice.hbs

<input type="text" oninput={{action "updateAnswer" value="target.value"}} />
{{#if showSolution}}
	<span style="color: red;">{{@question.solution}}</span>
{{/if}}
{{yield answer}}

templates.components.quiz-question.hbs

{{@question.name}}
{{#component
	(concat "quiz-" @question.type)
  question=@question
  showSolution=showSolution
as |answer|}}
	{{#if @question.quiz.test}}
  	{{yield answer}}
  {{else}}
		<button {{action "save" answer}} >verify</button>
  {{/if}}
{{/component}}

twiddle.json

{
  "version": "0.15.1",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.js",
    "ember": "3.4.3",
    "ember-template-compiler": "3.4.3",
    "ember-testing": "3.4.3"
  },
  "addons": {
    "ember-data": "3.4.2"
  }
}