Knockout / Select2：在下拉菜单中无法正常使用图书传输应用程序的问题

Question

所以我在尝试完成的应用程序遇到麻烦。它应该发送一份我想要拥有的书籍的更改列表。现在，我在剔除模型中有几个viewmodel，其中包含已通过json传递的数据。

我一直在尝试用正确的列表填充下拉列表，并跟踪发生的更改，但是我没有任何运气。这是我一直试图用来将列表附加到下拉列表的绑定。我可以填充它们，但是我什么也不能选择。

 function BookPossessionTransferVM() {
    var self = this;
    self.AllFromList = ([
      {"IsAdult":false,"Name":"Bob","ID":38438}, 
      {"IsAdult":false,"Name":"Gordon","ID":54686}
    ]);
    self.PossessionChanges  = ko.observableArray([]);
    self.PossessionChanges.push(new PossessionChangeModel());
    self.AvailableFrom = ko.computed(function() {
      var possessionChangesValues = self.PossessionChanges(),
          available = ko.utils.arrayFilter(self.AllFromList, function(selectedPerson) {
            return !ko.utils.arrayFirst(possessionChangesValues , function (possessionChange) {
              if (possessionChange.SelectedFrom() !== undefined) {
                return possessionChange!= self && 
                       possessionChange.SelectedFrom().Name() === selectedPerson.Name;
              } else {
                return false;
              }});
          });
      return available;
    });
    self.AvailableTo = ko.computed(function() {
       var possessionChangesValues = self.PossessionChanges(),
          available = ko.utils.arrayFilter(self.AllToList, function(selectedPerson) {
            return !ko.utils.arrayFirst(possessionChangesValues , function (possessionChange) {
              if (possessionChange.SelectedFrom() !== undefined) {
                return possessionChange!= self && 
                       possessionChange.SelectedFrom().Name() === selectedPerson.Name;
              } else {
                return false;
              }});
          });
      return available;
    });
    self.addPossessionChange = function () {
      self.PossessionChanges.push(new PossessionChangeModel());
    }
    self.removePossessionChangeChange = function(possessionChange) {
      self.PossessionChanges.remove(possessionChange);
    }
}

function PossessionChangeModel() {
    var self = this;
    self.SelectedFrom = ko.observable(new SelectedPerson());
    self.SelectedTo = ko.observable(new SelectedPerson());
    self.ChangeType = ko.pureComputed(function() {
      if (self.SelectedFrom() !== undefined && self.SelectedTo() !== undefined) {
        return 'Update';
      } else if (self.SelectedFrom() === undefined && self.SelectedTo() === undefined) {
          return '';
      } else if (self.SelectedFrom() === undefined) {
        return 'Add';
      } else if (self.SelectedTo() === undefined) {
        return 'Remove';
      } else { return ''; }
    });
}

function SelectedPerson() {
  var self = this;

  self.IsAdult  = ko.observable(false);
  self.Name = ko.observable("None");
  self.ID = ko.observable(0);
}
 
 ko.bindingHandlers.select2 = {
    init: function (element, valueAccessor, allBindingsAccessor, bindingContext) {
      ko.utils.domNodeDisposal.addDisposeCallback(element,
        function() {
          $(element).select2('destroy');
        });
      var select2 = ko.utils.unwrapObservable(allBindingsAccessor().options);
      $(element).select2(select2);
    },
    update: function (element, valueAccessor, allBindingsAccessor, bindingContext) {
      var allBindings = allBindingsAccessor();
      if ("value" in allBindings) {
        if ((allBindings.select2.multiple || element.multiple) && allBindings.value().constructor != Array) {
          $(element).val(allBindings.value().split(',')).trigger('change');
        } else {
          $(element).on('select2:selecting', function(e) {
              var data = e.params.args.data.id;
              console.log(data);
            });
          $(element).val(allBindings.value()).trigger('change');
        }
      }
      $(element).trigger("change");
    }
};
  
ko.applyBindings(new BookPossessionTransferVM());

  #tblPossessionChanges {
    width: 70%;
    height: 100px;
    text-align: center;
    table-layout: fixed;
  }

  #tblReassignChanges td, #tblPossessionChanges th {
    padding: 1rem;
  }

  #tblReassignChanges thead th {
    text-align: center;
  }

  #tblReassignChanges thead th:first-child {
    text-align: left;
    width: 10%;
  }

  #tblReassignChanges tbody td:first-child {
    text-align: left;
    width: 10%;
  }

  #tblReassignChanges > tbody > tr > td.prompt > a{
    font-weight: bold;
  }

  #tblReassignChanges tbody td select{
    width: 75%
  }

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/knockout/3.4.2/knockout-min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/select2/4.0.12/js/select2.full.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/3.3.7/js/bootstrap.min.js"></script>
<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/3.3.7/css/bootstrap.min.css" />
<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/select2/4.0.12/css/select2.min.css" />
<div>
  <table id="tblReassignChanges">
    <thead>
      <tr>
        <th><a href="#" class="buttonSmall" data-bind="click: addPossessionChange">Add</a></th>
        <th>From</th>
        <th>To</th>
      </tr>
    </thead>
    <tbody data-bind="foreach: PossessionChanges">
      <tr>
        <td class="prompt">
          <a href="#" class="buttonSmall" data-bind="click: $root.removePossessionChange">Delete</a>           </td>
        <td>
          <select class="form-control" 
                  data-bind="options: $root.AvailableFrom, 
                             value: SelectedFrom,
                             optionsText: 'Name', 
                             optionsValue: 'ID',
                             select2: { placeholder: 'Please select a Person...', allowClear: true}">             </select>
        </td>
        <td>
          <select class="form-control"
                  data-bind="options: $root.AvailableTo, 
                             value: SelectedTo, 
                             optionsText: 'Name', 
                             optionsValue: 'ID',
                             select2: {placeholder: 'Please select a Person...', allowClear: true}">            </select>
        </td>
        <td>
          <span id="changeTypeSpan" data-bind="text: ChangeType"></span>
        </td>
      </tr>
    </tbody>
  </table>
</div>

我也尝试过将optionsValue更改为使用ID，但随后将覆盖我拥有的selectedPerson对象。我愿意接受所有建议和帮助。谢谢！

编辑：这是jsFiddle，它复制了我的问题，从而节省了空间。我也对数据进行了硬编码。 https://jsfiddle.net/3upb0mf8/5/

Answer 1

您在这里有多个问题：

1. 主要问题是，您假定possessionChange.SelectedFrom()包含整个人员对象，而实际上它仅包含其ID，因为这就是传递给optionsValue的内容。请read this answer完全了解它。您必须按其ID检索此人。
2. [AvailableTo指的是possessionChange.SelectedFrom()，而不是possessionChange.SelectedTo()。
3. 名称冲突：removePossessionChange与removePossessionChangeChange。
4. A PossesionChange必须具有ID，以便可以将其删除。

以及其他一些问题。

我想我已经解决了大多数问题。另请注意，我使用的是PersonVM而不是普通对象：

function BookPossessionTransferVM() {
  var self = this;
  self.All = [new PersonVM(false,"Bob",38438), new PersonVM(false,"Gordon",54686)];
  self.PossessionChanges  = ko.observableArray([]);
  self.AvailableFrom = ko.computed(function() {
    var available = ko.utils.arrayFilter(self.All, function(item) {
      return !ko.utils.arrayFirst(self.PossessionChanges() , function (possessionChange) {
         var person = self.getPersonById(possessionChange.SelectedFrom());
         if (person) {

          return person.Name() === item.Name();
         } else {
           return false;
         }
      });
    });
    return available;
  });
  self.AvailableTo = ko.computed(function() {
    var available = ko.utils.arrayFilter(self.All, function(item) {
      return !ko.utils.arrayFirst(self.PossessionChanges() , function (possessionChange) {
        var person = self.getPersonById(possessionChange.SelectedTo());
         if (person) {
          return person.Name() === item.Name();
        } else {
          return false;
        }});
    });
    return available;
  });
  self.getPersonById = function (id) {
    return ko.utils.arrayFirst(self.All, function(person){
          return person.ID === id;
      });
  }
  self.addPossessionChange = function () {
    self.PossessionChanges.push(new PossessionChangeVM(self.PossessionChanges.length + 1));
  }
  self.removePossessionChange = function(possesion) {
    self.PossessionChanges.remove(function (item) {
      return possesion.possesionId() == item.possesionId();
    });
  }
}

function PossessionChangeVM(possesionId) {
  var self = this;
  self.possesionId = ko.observable(possesionId);
  self.SelectedFrom = ko.observable();
  self.SelectedTo = ko.observable();
  self.ChangeType = ko.pureComputed(function() {
    if (self.SelectedFrom() !== undefined && self.SelectedTo() !== undefined) {
      return 'Update';
    } else if (self.SelectedFrom() === undefined && self.SelectedTo() === undefined) {
        return '';
    } else if (self.SelectedFrom() === undefined) {
      return 'Add';
    } else if (self.SelectedTo() === undefined) {
      return 'Remove';
    } else { return ''; }
  });
}

function PersonVM(isAdult, name, id) {
  var self = this;

  self.IsAdult  = ko.observable(isAdult);
  self.Name = ko.observable(name);
  self.ID = ko.observable(id);
}
 ko.bindingHandlers.select2 = {
  init: function (element, valueAccessor, allBindingsAccessor, bindingContext) {
    ko.utils.domNodeDisposal.addDisposeCallback(element,
      function() {
        $(element).select2('destroy');
      });
    var select2 = ko.utils.unwrapObservable(allBindingsAccessor().options);
    $(element).select2(select2);
  },
  update: function (element, valueAccessor, allBindingsAccessor, bindingContext) {
    var allBindings = allBindingsAccessor();
    if ("value" in allBindings) {
      if ((allBindings.select2.multiple || element.multiple) && allBindings.value().constructor != Array) {
        $(element).val(allBindings.value().split(',')).trigger('change');
      } else {
        $(element).on('select2:selecting', function(e) {
            var data = e.params.args.data.id;
          });
        $(element).val(allBindings.value()).trigger('change');
      }
    }
    $(element).trigger("change");
  }
};
ko.applyBindings(new BookPossessionTransferVM());

#tblPossessionChanges {
    width: 70%;
    height: 100px;
    text-align: center;
    table-layout: fixed;
  }

  #tblReassignChanges td, #tblPossessionChanges th {
    padding: 1rem;
  }

  #tblReassignChanges thead th {
    text-align: center;
  }

  #tblReassignChanges thead th:first-child {
    text-align: left;
    width: 10%;
  }

  #tblReassignChanges tbody td:first-child {
    text-align: left;
    width: 10%;
  }

  #tblReassignChanges > tbody > tr > td.prompt > a{
    font-weight: bold;
  }

  #tblReassignChanges tbody td select{
    width: 75%
  }

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/knockout/3.4.2/knockout-min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/select2/4.0.12/js/select2.full.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/3.3.7/js/bootstrap.min.js"></script>
<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/3.3.7/css/bootstrap.min.css" />
<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/select2/4.0.12/css/select2.min.css" />
<div>
  <table id="tblReassignChanges">
    <thead>
      <tr>
        <th><a href="#" class="buttonSmall" data-bind="click: addPossessionChange">Add</a></th>
        <th>From</th>
        <th>To</th>
      </tr>
    </thead>
    <tbody data-bind="foreach: PossessionChanges">
      <tr>
        <td class="prompt">
          <a href="#" class="buttonSmall" data-bind="click: $root.removePossessionChange">Delete</a>           </td>
        <td>
          <select class="form-control" 
                  data-bind="options: $root.AvailableFrom, 
                             value: SelectedFrom,
                             optionsText: 'Name', 
                             optionsValue: 'ID',
                             select2: { placeholder: 'Please select a Person...', allowClear: true}">             </select>
        </td>
        <td>
          <select class="form-control"
                  data-bind="options: $root.AvailableTo, 
                             value: SelectedTo, 
                             optionsText: 'Name', 
                             optionsValue: 'ID',
                             select2: {placeholder: 'Please select a Person...', allowClear: true}">            </select>
        </td>
        <td>
          <span id="changeTypeSpan" data-bind="text: ChangeType"></span>
        </td>
      </tr>
    </tbody>
  </table>
</div>