淘汰赛无法处理绑定 [英] Knockout unable to process binding

问题描述

当文本未定义时如何绑定文本?例如，名称不可用:

How do I bind a text when it is undefined? For example name is not available:

<table id="recordTbl" data-bind="visible: records().length &gt; 0" class="table">
  <thead>
    <tr>
      <th class="col-md-4">ID</th>
      <th class="col-md-4">Name</th>
    </tr>
  </thead>
  <tbody data-bind="foreach: records">
    <tr>
      <td data-bind="text: id"></td>
      <td data-bind="text: name"></td>
    </tr>
  </tbody>
</table>

我收到此错误:

Uncaught ReferenceError: Unable to process binding "text: function (){return name }"
Message: name is not defined 

推荐答案

您可以使用$data绑定上下文属性，该属性始终代表当前视图模型以通过它访问name:

You can you the $data binding context property which always represents the current view model to access the name through it:

  <tbody data-bind="foreach: records">
    <tr>
      <td data-bind="text: id"></td>
      <td data-bind="text: $data.name"></td>
    </tr>
  </tbody>

使用这种方法，如果records中的一项不具有name属性，则KO不会引发异常.

With this approach KO won't throw an exception if one of the items in the records does not have a name property.

没有$data，则未定义名为name的标识符.但是$data.name始终是有效的表达式，如果当前视图模型没有名为name的属性，它只会返回undefined.

Without the $data the identifier named name is undefined. However $data.name is always a valid expression it just returns undefined if the current view model does not have a property named name.

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