动态生成的下拉列表选项的挖空绑定

Knockout binding of a Dynamically generated Dropdown options

本文关键字：绑定 选项 下拉列表 动态      更新时间：2023-09-26

我有 2 个下拉列表。两者都通过挖空进行数据绑定。我试图在这里实现两件事：第一个下拉菜单是认证，第二个下拉菜单是专业化。

  1. 默认情况下，第二个下拉列表应将"请选择专业化"作为未发生的选项。它发生在第一个下拉列表。我想我知道为什么。也许是因为认证是一个可观察的数组，它通过options绑定进行数据绑定。

  2. 不幸的是，我不能对第二个下拉列表执行相同的操作，因为它的值将取决于第一个下拉列表。即使我已经为第二个下拉列表提供了optionsCaption，但在页面加载时我仍然看不到它。

$(document).ready(function () {
    var Provider = {
        ProviderID: ko.observable(""),
        FirstName: ko.observable(""),
        LastName: ko.observable(""),
        Certification: ko.observableArray(["M.B.B.S", "M.D.", "R.N.", "M.S.N."]),
        SelectedCertification: ko.observable(""),
        Specialization: ko.observable(""),
        TaxonomyCode: ko.observable(""),
        SSN: ko.observable(""),
        ContactNumber: ko.observable(""),
        ContactEmail: ko.observable(""),
        NPI: ko.observable("")
    };
    ko.applyBindings(Provider);
    $("#Certification").change(function () {
        if (($("#Certification").val() == "M.D.") || ($("#Certification").val() == "M.B.B.S")) {
            $("#Err_Certification").hide();
            $("#Certification").removeClass('borderclass');
            $("<option>Dermatology</option>").appendTo("#Specialization");
            $("<option>Hematology</option>").appendTo("#Specialization");
            $("<option>Neurology</option>").appendTo("#Specialization");
        } else if (($("#Certification").val() == "R.N.") || ($("#Certification").val() == "M.S.N.")) {
            $("#Err_Certification").hide();
            $("#Certification").removeClass('borderclass');
            //$("#Certification option[value='option1']").remove();
            //$("#Certification option[value='option2']").remove();
            //$("#Certification option[value='option3']").remove();
            $("<option>Pediatric Nursing</option>").appendTo("#Specialization");
            $("<option>Critical Care Nursing</option>").appendTo("#Specialization");
            $("<option>Occupational Health Nursing </option>").appendTo("#Specialization");
        } else {
            $("#Specialization").addClass('borderclass');
            $("#Err_Specialization").show();
        }
    });
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.3/jquery.min.js"></script>
<script src="https://ajax.googleapis.com/ajax/libs/jqueryui/1.11.2/jquery-ui.min.js"></script>
<script src="//maxcdn.bootstrapcdn.com/bootstrap/3.3.2/js/bootstrap.min.js"></script>
<script src="//maxcdn.bootstrapcdn.com/bootstrap/3.3.2/css/bootstrap.min.css"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery-validate/1.13.1/jquery.validate.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/knockout/3.2.0/knockout-min.js"></script>
<div class="container">
  <form class="form-horizontal">
    <div class="form-group">
      <label class="col-sm-2 control-label labelfont">CERTIFICATION:</label>
      <div class="col-sm-6">
        <select class="form-control" id="Certification" name="Certification" data-bind="value: SelectedCertification, options: Certification, optionsCaption: 'Select a Certification'">
        </select>
      </div>
    </div>
    <div class="form-group">
      <label class="col-sm-2 control-label labelfont">SPECIALIZATION:</label>
      <div class="col-sm-6">
        <select class="form-control" id="Specialization" name="Specialization" data-bind="value: Specialization, optionsCaption: 'Select a Specialization'">
        </select>
      </div>
    </div>
  </form>
</div>

我分叉了jquery更改和一些代码并引入了subscribe。

查看型号 ： 

  var Provider = function () {
          var self = this;
          self.Certification = ko.observableArray(["M.B.B.S", "M.D.", "R.N.", "M.S.N."]);
          self.SpecialzationArray = ko.observableArray();
          self.SelectedCertification = ko.observable();
          self.Specialization = ko.observable();
          self.SelectedCertification.subscribe(function (val) {
            self.SpecialzationArray([]);
              if (val == "M.D." || val == "M.B.B.S") {
                  self.SpecialzationArray(["Dermatology", "Hematology", "Neurology"])
              } else if (val == "R.N." || val == "M.S.N.") {
                  self.SpecialzationArray(["Pediatric Nursing", "Critical Care Nursing", "Occupational Health Nursing"])
              } else {
                  self.SpecialzationArray([]);
              }
          });
      };
      $(document).ready(function () {
          ko.applyBindings(new Provider());
      });

视图：

<select data-bind="value: SelectedCertification, options: Certification, optionsCaption: 'Select a Certification'"></select>
<br/>
<select data-bind="value: Specialization,options:SpecialzationArray, optionsCaption: 'Select a Specialization'"></select>

当我订阅 DDL1 的绑定时下拉列表中有变化value我们可以有条件地填充 dropdown2 所需的数据。

对于工作小提琴，请单击此处

保持视图模型干净总是更好，这在处理复杂场景时会有所帮助。

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