为什么我的 this._setPropertyName 功能不起作用？

Question

我有以下聚合物元素：

<link rel="import" href="../../bower_components/polymer/polymer.html">
<link rel="import" href="../../bower_components/polymer/polymer-element.html">
<link rel="import" href="../shared-styles.html">
<link rel="import" href="../../bower_components/dfw-styles/dfw-styles.html">
<link rel="import" href="../../bower_components/paper-button/paper-button.html">
<link rel="import" href="../../bower_components/paper-menu-button/paper-menu-button.html">
<link rel="import" href="../../bower_components/paper-listbox/paper-listbox.html">

<dom-module id="baseline-policy-create">
  <template>
    <style include="dfw-styles">
      :host {
        display: block;
      }
      .top-button{
        float : right;
      }
    </style>

    <div class="outer-buttons">
      <paper-menu-button horizontal-align="right" no-overlap="true" no-animations class="top-button">
        <paper-button slot="dropdown-trigger" class="dropdown-trigger create-button btn-primary">
          <iron-icon icon="menu"></iron-icon>
          <span>Create Baseline Policy</span>
        </paper-button>
        <paper-listbox slot="dropdown-content" class="dropdown-content">
          <template is="dom-repeat" items="{{_domains}}">
            <paper-item on-tap="getDomainSchema">[[item.label]]</paper-item>
          </template>
        </paper-listbox>
      </paper-menu-button>
    </div>
  </template>
  <script>
    class BaselinePolicyCreate extends Polymer.Element {
      static get is() {
        return 'baseline-policy-create';
      }

      static get properties() {
        return {
          _domains: {
            type: Array,
            value: [{'name':'Package', 'label':'Package'},
                    {'name':'Subscription', 'label':'Subscription'}] //TODO: is it possible to get these values from an API source
          },
          requestedDomain: {
            type: String,
            value : "",
            notify : true,
            readOnly : true
          }
        }
      }

      getDomainSchema(evt) {
        console.info("Get the schema for the following domain:", evt.target.innerText);
        console.log(this.requestedDomain);
        this._setRequestedDomain(evt.target.innerText);
        //this.requestedDomain = evt.target.innerText;
        console.log(this.requestedDomain);
      }
    }
    customElements.define(BaselinePolicyCreate.is, BaselinePolicyCreate);
  </script>
</dom-module>

我一直在关注这个关于数据绑定的教程：https://www.tutorialspoint.com/polymer/polymer_data_system.htm

在示例中，prop-element 的代码有一个属性，myProp，其属性 readOnly 设置为 true。在 Onclick 函数中，它仍然能够使用未在任何地方明确定义的 this._setMyProp() 更改属性的值。

我想在我的代码中做同样的事情。也就是说，我想使用此方法设置 requestedDomain。我可以使用这一行来设置它：

this.requestedDomain = evt.target.innerText;

但是要这样做，我不能将 readOnly 标志设置为 true。如果我使用 this._setRequestedDomain，我会收到一条错误消息，指出它不是一个函数。我是否在顶部缺少一些导入以允许它工作，或者它可能已在 Polymer 2 中删除？

Answer 1

我一直在测试你的代码，没问题。

You only will get the error "this.setRequestedDomain is not a function" if your property is set as readOnly = false.

Please, try again and tell me if its ok.

pen code example (without styling)

为什么我的 this._setPropertyName 功能不起作用？

Why doesn't my this._setPropertyName function work?

polymer

polymer-2.x