Polymer1.x：预加载元素属性

Question

我正在尝试使用 ['Colorado', 'South Dakota'] 的 selected 属性的预定义值加载我的元素。

我希望看到页面加载带有所有 U.S 轮廓的地图。状态。控制台中没有错误。科罗拉多州和南达科他州预选并涂成蓝色。

相反，我在控制台中看到一个空白页面（根本没有地图）和一组错误，开头如下：

console.error

Polymer::Attributes: couldn't decode Array as JSON

以下步骤将重现问题：

Open this jsBin.
注意地图在输出窗格中正确加载。（并在选择和取消选择状态时正常工作。）
向下滚动到页面底部的 <x-element> 标签。
删除 selected 属性前面的 x 字符，这样完整的属性显示为：selected="['Colorado', 'South Dakota']".
请注意地图消失了，不再正确加载并且上述错误出现在控制台中。
替换您刚刚删除的 x 并注意地图加载并再次正常工作。

问题

这里可能发生了什么？是什么导致了这个问题，什么可以解决它？如果可以，请包括您的解决方案的有效 jsBin 示例。

http://jsbin.com/qupoleveja/1/edit?html,控制台,输出

<!DOCTYPE html>

<head>
  <meta charset="utf-8">
  <base href="https://polygit.org/components/">
  <script src="webcomponentsjs/webcomponents-lite.min.js"></script>
  <link href="polymer/polymer.html" rel="import">
  <link href="google-chart/google-chart.html" rel="import">
</head>

<body>

  <dom-module id="x-element">

    <template>
      <style>
        google-chart {
          width: 100%;
          max-height: 300px;
        }
      </style>
      <button on-tap="_show">Show</button>
      <div>[[selected]]</div>
      <google-chart
        id="geochart"
        type="geo"
        options="{{options}}"
        data="{{items}}"
        xon-google-chart-select="_onGoogleChartSelect"></google-chart>
    </template>

    <script>
      (function(){
        Polymer({
          is: 'x-element',
          /** /
           * Fired when user selects chart item.
           *
           * @event us-map-select
           * @param {object} detail Alpabetized array of selected state names.
          /**/
          properties: {
            selected: {
              type: Array,
              notify: true,
              //reflectToAttribute: true,
            },
            items: {
              type: Array,
              notify: true,
              reflectToAttribute: true,
            },
            color: {
              type: String, // '#455A64'
              value: function() {
                return 'blue';
              }
            },
            options: {
              type: Object,
              notify: true,
              reflectToAttribute: true,
              computed: '_computeOptions(color)'
            },
            itemIndices: {
              type: Object,
              computed: '_computeItemIndices(items)',
            },
          },

          observers: [
            '_selectedChanged(selected.*)'
          ],

          ready: function() {
            var a = [['State', 'Select'], ['Alabama', 0], ['Alaska', 0], ['Arizona', 0], ['Arkansas', 0], ['California', 0], ['Colorado', 0], ['Connecticut', 0], ['Delaware', 0], ['Florida', 0], ['Georgia', 0], ['Hawaii', 0], ['Idaho', 0],  ['Illinois', 0], ['Indiana', 0], ['Iowa', 0], ['Kansas', 0], ['Kentucky', 0], ['Louisiana', 0], ['Maine', 0], ['Maryland', 0], ['Massachusetts', 0], ['Michigan', 0], ['Minnesota', 0], ['Mississippi', 0], ['Missouri', 0], ['Montana', 0], ['Nebraska', 0], ['Nevada', 0], ['New Hampshire', 0], ['New Jersey', 0], ['New Mexico', 0], ['New York', 0], ['North Carolina', 0], ['North Dakota', 0], ['Ohio', 0], ['Oklahoma', 0], ['Oregon', 0], ['Pennsylvania', 0], ['Rhode Island', 0], ['South Carolina', 0], ['South Dakota', 0], ['Tennessee', 0], ['Texas', 0], ['Utah', 0], ['Vermont', 0], ['Virginia', 0], ['Washington', 0], ['West Virginia', 0], ['Wisconsin', 0], ['Wyoming', 0]];
            this.set('items', a);
            var _this = this; 
            this.$.geochart.addEventListener('google-chart-select',function(e){this._onGoogleChartSelect(e)}.bind(_this));
          },

          _computeItemIndices: function(a) {
            var out = {},
                i = a.length;
            while(i--){
              out[a[i][0]] = i;
            }
            return out;
          },

          _onGoogleChartSelect: function(e) {
            var str = e.path[0].textContent.split('Select')[0].trim(), // e.g. 'Ohio'
                temp = [],
                ar = this.items,
                index = this.itemIndices[str], // e.g. 35
                i = ar.length;
            this.set('items.' + index + '.1', ar[index][1] ? 0 : 1);
            while(i---1){
              /** /
              if(str === ar[i][0]){
                this.set('items.' + i + '.1', ar[i][1] ? 0 : 1);
                //this.items[i][1] = ar[i][1] ? 0 : 1;
              }
              /**/
              if(ar[i][1]){
                temp.push(ar[i][0]);
              }
            }
            temp.sort();
            this.set('selected', temp);
            this._drawChart();
            //console.log(this.selected);
          },

          _drawChart: function() {
            this.$.geochart._dataTable=this.$.geochart._createDataTable(this.items);
            this.$.geochart._chartObject.draw(this.$.geochart._dataTable,
                                              this.$.geochart.options);
          },

          doAll: function(verb) {
            verb = verb || 'clear'; // verb: 'clear'(default)|'select'
            verb = (verb === 'select') ? 'select' : 'clear';
            this._doAll(verb);
            this._drawChart();
          },

          _doAll: function(verb) {
            var resetSelect = (verb && verb === 'some') ? false : true;
            verb = verb || 'clear'; // verb: 'clear'(default)|'select'|'some'
            verb = (verb === 'select') ? 'select' : 'clear';
            var temp = [],
                items = this.items,
                i = items.length;
            switch(verb) {
              case 'select':
                while(i---1){
                  items[i][1] = 1;
                  temp.push(items[i][0]);
                }
                break;
              case 'clear':
                while(i---1){
                  items[i][1] = 0;
                }
                break;
              default:
                break;
            }
            this.set('items', items);
            if(resetSelect){
              temp.sort();
              this.set('selected', temp);
            }
          },

          _selectedChanged: function(ar) {
            var a = ar.base,
                i = a.length;
            this._doAll('some');
            while(i--){
              var index = this.itemIndices[a[i]];
              this.set('items.' + index + '.1', 1);
            }
            this._drawChart();
            this.fire('us-map-select',this.selected)
            console.log(this.selected);
          },

          _computeOptions: function() {
            return {
              region: 'US',
              displayMode: 'regions',
              resolution: 'provinces',
              legend: 'none',
              defaultColor: '#F5F5F5',
              colorAxis: {
                colors: ['#F5F5F5', this.color],
                minValue: 0,  
                maxValue: 1,
              }
            }
          },

          _show: function(){
            //this.set('selected', ['Ohio', 'New Mexico']);
            this.doAll();
            //console.log(this.itemIndices);
          },
        });
      })();
    </script>

  </dom-module>

  <x-element xcolor="#455A64"
             xselected="['Colorado', 'South Dakota']" ></x-element>

</body>
</html>

Answer 1

我觉得应该是

selected='["Colorado", "South Dakota"]'

JSON 需要双引号。

Polymer1.x：预加载元素属性

Polymer 1.x: Pre-loading element attributes

javascript

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polymer

polymer-1.0

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