polymer 自定义元素属性作为 bool 类型值

Question

虽然 Demo A有效，我想了解是否可以使其像 Demo B 一样工作.基本上，要为自定义元素解析 happyFlag属性为 bool 类型。

// Demo A - works. bob smiles. cat frowns.
<x-smiley name="Bob" happyFlag="true"></x-smiley>
<x-smiley name="Cat" happyFlag="false"></x-smiley>
<polymer-element name="x-smiley" attributes="name, happyFlag" noscript>
    <template>
        {{name}} is
        <span hidden?="{{happyFlag == 'true'}}">:-)</span>
        <span hidden?="{{happyFlag == 'false'}}">:-(</span>
        <hr>
    </template>
</polymer-element>

// Demo B - does not work (span always hidden)
<x-smiley name="Bob" happyFlag="true"></x-smiley>
<x-smiley name="Cat" happyFlag="false"></x-smiley>
<polymer-element name="x-smiley" attributes="name, happyFlag" noscript>
    <template>
        {{name}} is
        <span hidden?="{{happyFlag}}">:-)</span>
        <span hidden?="{{happyFlag}}">:-(</span>
        <hr>
    </template>
</polymer-element>

Answer 1

您可以向 Polymer 提供有关属性是什么类型的输入的提示。请参阅以下示例，其中我添加了 Polymer 脚本，特别是 this.happyFlag = false在创建的方法中。该行提示 Polymer 应将此值视为 bool 值。见 Polymer's Documentation关于提示类型。

<polymer-element name="x-smiley" attributes="name, happyFlag">
<template>
    {{name}} is {{happyFlag}}
    <span hidden?="{{happyFlag}}">:-)</span>
    <span hidden?="{{happyFlag}}">:-(</span>
    <hr>
</template>
<script>
  Polymer('x-smiley', {
    created: function() {
        this.happyFlag = false;
    },
    ready: function() {
    }
  })
</script>