在Ember.js中，如何创建一个计算属性，该属性引用包含数组的属性中的第一项 [英] In Ember.js how do I create a computed property that references first item in property containing an array

问题描述

我有一个测验装置，它具有一个称为问题的属性，它是一组相关问题的ID。我想在名为firstQ的模型上创建一个计算属性，该属性返回问题数组中的第一个id。最终，我想使用该ID并将其链接到我创建的问题路由。

I have quiz fixtures that have a property called questions, which is an array of ids of associated questions. I want to create a computed property on the model called firstQ that returns the first id in the questions array. Ultimately I would like to take that id and use it to link to a question route I have created.

我不知道如何访问问题数组中的第一个ID。这甚至是解决此问题的最佳方法吗？请帮忙。

I can not figure out though, how to access that first id in the questions array. Is this even the best way to approach this? Please help.

App.ApplicationAdapter = DS.FixtureAdapter.extend();

App.Quiz = DS.Model.extend({
  name: DS.attr('string'),
  description: DS.attr('string'),
  questions: DS.hasMany('question', {async: true}),
  firstQ: function() {
    return this.get('questions')//where to go next?, on right track?;
  }.property()
});

App.Question = DS.Model.extend({
  question: DS.attr('string'),
  quiz: DS.belongsTo('quiz', {async: true}),
  answers: DS.attr('string')
});

//fixtures
App.Quiz.FIXTURES = [
  {
    id: 1,
    name: 'The JavaScript Quiz',
    description: 'take this quiz and find out if you\'re a super genious',
    questions: [100,101]
  }
];

App.Question.FIXTURES = [
  {
    id:100,
    question: 'Inside which HTML element do we put the JavaScript',
    quiz: 1,
    answers: [
      { answer: 'alpha', weight: 0 },
      { answer: 'beta', weight: 5 }
    ]
  }
]

推荐答案

好的，所以我找出如何通过模型上的计算属性来执行此操作。这是App.Quiz模型的更新代码：

Okay, so I figured out how to to do this via the computed property on the model. Here's the updated code for the App.Quiz model:

App.Quiz = DS.Model.extend({
  name: DS.attr('string'),
  description: DS.attr('string'),
  questions: DS.hasMany('question', {async: true}),
  firstQuestion: function() {
    return this.get('questions.firstObject');
  }.property('questions.firstObject')
});

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