Ember.Object实例中的必需属性(构造函数args)

Question

在Ember中,假设我有一个名为的对象FoodStuff具有一些属性:

export default Ember.Object.extend({
    name: null,     // REQUIRED: 'Slice of Apple Pie'
    calories: null, // OPTIONAL: int: eg. 250
    category: null, // REQUIRED: 'Pastry'
    rating: null    // OPTIONAL: int: 1-5
});

如何在Ember中编写"构造函数",要求在实例化时提供"名称"和"类别"属性？

Angular似乎用相当简单的语法来解决这个问题:

.factory('User', function (Organisation) {

  /**
   * Constructor, with class name
   */
  function User(firstName, lastName, role, organisation) {
    // Public properties, assigned to the instance ('this')
    this.firstName = firstName;
    ...

具有JavaScript类的Angular模型对象

Ember有类似的东西吗？目前我的所有类都在顶部看到,有一堆初始为null的属性,调用者可能正确设置也可能没有.在构建时(我正在使用ember-cli),我希望在ember buildJSHint阶段的下游捕获构造函数需求的更改.

Answer 1

据我所知，Ember 中没有本地方法可以做到这一点。但没有什么是不可能的！您可以稍微调整 Ember 来处理这种情况。只需添加一个初始化程序：

/initializers/extend-ember.js：

import Ember from 'ember';

export function initialize() {

  Ember.Object.reopen({

    /**
     * @prop {Array} - array of required properties
     */
    requiredAttrs: [],

    /**
     * Validates existance of required properties
     *
     * @param {String} attr - attribute name
     * @param {*} value - value of the property
     * @throws {Error} in case when required property is not set
     */
    _validateExistance(attr, value) {
      if (this.requiredAttrs.contains(attr) && typeof value === "undefined") {
        throw new Error("Attribute " + attr + " can't be empty!");
      }
    },

    /**
     * Sets value of a property and validates existance of required properties
     *
     * @override 
     */
    set(key, value) {
      this._validateExistance(key, value);
      return this._super(key, value);
    }

  });

  Ember.Object.reopenClass({

    /**
     * Creates object instance and validates existance of required properties
     *
     * @override
     */
    create(attrs) {
      let obj = this._super(attrs);
      if (attrs) {
        obj.requiredAttrs.forEach((key) => {
          obj._validateExistance(key, attrs[key]);
        });
      }
      return obj;
    }

  });

}

export default {
  name: 'extend-ember',
  initialize: initialize
};

然后，您可以使用requiredAttrs任何类上的属性来定义需要哪些属性。如果您尝试创建具有空必需属性的实例，或者尝试将空值设置为必需属性，它将引发异常。

let MyModel = Ember.Object.extend({
  prop1: null,
  prop2: null,
  requiredAttrs: ['prop2']
});

let ChildModel = MyModel.extend({
  prop3: null,
  requiredAttrs: ['prop2', 'prop3']
});

// throws exception
let obj1 = MyModel.create({
  prop1: 'val1'
});

// no exception
let obj2 = MyModel.create({
  prop2: 'val2'
});

// throws exception
obj2.set('prop2', undefined);

// throws exception
let obj3 = ChildModel.create({
  prop3: 'val3'
});

// no exception
let obj4 = ChildModel.create({
  prop2: 'val2',
  prop3: 'val3'
});

它也适用于DS.Model开箱即用的其他 Ember 实体，因为它们都扩展了Ember.Object.