Question

我有一个相当简单的对象数组，可以在KO中编辑

Here's a test case. 尝试点击这些项目并在下面进行编辑。它有效。

...然而

加载到数组中的数据来自JSON字符串：

 self.text = ko.observable('[{ "value": "1", "text": "Low" }, ..... ]');

必须将其解析并转换为JS对象。这在计算函数中完成，如下所示：

 self.ssArray = ko.computed({
    read: function() {

        // Convert text into JS object
        // Not using ko.utils because I want to use try/catch to detect bad JS later

        var arrayJS = JSON.parse(ko.utils.unwrapObservable(self.text));

        // Make an array of observables
        // Not using ko.mapping in order to get back to basics
        // Also mapping function throws an error re: iterations or something

        var obsArrayJS = ko.utils.arrayMap(arrayJS, function(i) {
            return {
                "value": ko.observable(i.value),
                "text": ko.observable(i.text)
            };
        });

        // return array of objects with observable properties.
        return obsArrayJS;

        // Tried this but made no difference:
        //return ko.observableArray(obsArrayJS);
    },

现在我想要的是在更新模型时更新原始文本字符串。它应该是模型上ko.toJSON的一个简单例子：

 write: function(value) {
        self.text(ko.toJSON(this.ssArray));
    },

正如您从小提琴中看到的那样，self.text未更新。

为什么会这样？

我尝试了以下内容：

从read函数返回observableArray - 没有区别
返回一个observableArray的可观察对象，每个对象都有可观察的属性
使用映射插件使所有内容都可观察

我想这可以归结为KO如何解释写入函数。当然，如果ssArray的内容发生了变化，那么write会被解雇吗？但不是我的情况......

可能的进一步复杂性是这将是一个KO组件。文本输入实际上来自于从窗口小部件传递的参数。所以我猜它已经是一个可观察的？所以它还需要更新父视图模型。

除此之外，我正在尝试使用可排序插件来重新排序这些项目 - 但我已将其从测试用例中删除。

Answer 1

＆＃39>写＆＃39;你的计算机的函数没有触发，因为你没有写入计算机 - 这意味着在某处调用ssArray(some_value)。

这是另一种有效的解决方案：

我们为单个文本/值对

items

通过手动调用loadJSON填充此observableArray。
我们创建一个计算器，通过遍历它们来建立对items observableArray以及所有项text和value可观察项的订阅。无论何时添加或删除或更改任何项目，我们都会将整个数组序列化为JSON

您当然可以订阅self.text并自动触发loadJSON，但是您必须处理“文字”的圈子＆＃39;触发＆＃39; loadJSON＆＃39;，触发我们的计算，写回text。

（我隐藏了代码片段以摆脱HTML和CSS代码块。点击＆＃34;显示代码片段＆＃34;运行示例。）

    function MyViewModel() {

        var self = this;

        this.selectedItemSS = ko.observable();
        this.setSelectedSS = function(item) {
            self.selectedItemSS(item);
        };

        // Data in text form. Passed in here as a parameter from parent component
        this.text = ko.observable('[{"value": "1", "text": "Low"}, {"value": "2", "text": "Medium"}, {"value": "3", "text": "High"} ]');

        this.items = ko.observableArray([]);

        this.loadJSON = function loadJSON(json) {
            var arrayOfObjects = JSON.parse(json),
                arrayOfObservables;

            // clear out everything, or otherwise we'll end
            // up with duplicated objects when we update
            self.items.removeAll();

            arrayOfObservables = ko.utils.arrayMap(arrayOfObjects, function(object) {
                return {
                    text:  ko.observable(object.text),
                    value: ko.observable(object.value)
                };
            });

            self.items(arrayOfObservables);
        };

        this.loadJSON( this.text() );

        ko.computed(function() {
            var items = this.items();

            // iterate over all observables in order
            // for our computed to get a subscription to them
            ko.utils.arrayForEach(items, function(item) {
                item.text();
                item.value();
            });

            this.text(ko.toJSON(items));

        }, this);
    }

    ko.applyBindings(new MyViewModel());

＆＃13;

    function MyViewModel() {
    
        var self = this;
        
        this.selectedItemSS = ko.observable();
        this.setSelectedSS = function(item) {
            self.selectedItemSS(item);
        };
    
        // Data in text form. Passed in here as a parameter from parent component
        this.text = ko.observable('[ \
      {\
        "value": "1",\
        "text": "Low"\
      },\
      { \
       "value": "2",\
        "text": "Medium"\
      },\
      {\
        "value": "3",\
        "text": "High"\
      } ]');
        
        this.items = ko.observableArray([]);
        
        this.loadJSON = function loadJSON(json) {
            var arrayOfObjects = JSON.parse(json),
                arrayOfObservables;
            
            // clear out everything, or otherwise we'll end
            // up with duplicated objects when we update
            self.items.removeAll();
            
            arrayOfObservables = ko.utils.arrayMap(arrayOfObjects, function(object) {
                return {
                    text:  ko.observable(object.text),
                    value: ko.observable(object.value)
                };
            });
            
            self.items(arrayOfObservables);
        };
        
        this.loadJSON( this.text() );
        
        ko.computed(function() {
            var items = this.items();
            
            // iterate over all observables in order
            // for our computed to get a subscription to them
            ko.utils.arrayForEach(items, function(item) {
                item.text();
                item.value();
            });
            
            this.text(ko.toJSON(items));
            
        }, this);
    }
    
    ko.applyBindings(new MyViewModel());

＆＃13;

body { font-family: arial; font-size: 14px; }
.well {background-color:#eee; padding:10px;}

pre {white-space:pre-wrap;}

＆＃13;

<script src="https://cdnjs.cloudflare.com/ajax/libs/knockout/3.2.0/knockout-min.js"></script>
<h3>Text Json: eg from AJAX request</h3>
<p>In practice this comes from a parent custom component as a parameter</p>
<pre class="well" data-bind="text:text"></pre>
<h3>Computed data model</h3>
<p>Click on an item to edit that record</p>
<div data-bind="foreach:items" class="well">
    <div data-bind="click: $parent.setSelectedSS">    
    <span data-bind="text:value"></span>
    <span data-bind="text:text"></span><br/>
    </div>
</div>
<hr/>
<h3>Editor</h3>
<div data-bind="with:selectedItemSS" class="well">
       <input data-bind="textInput:value"/>
    <span data-bind="text:value"></span><br/>
</div>

＆＃13;

如果您愿意，这里有一个替代版本，可以处理JSON的更改以及通过单个计算机对接口进行编辑：

function MyViewModel(externalObservable) {
  var self = this;

  this.selectedItemSS = ko.observable();
  this.setSelectedSS  = function(item) {
    self.selectedItemSS(item);
  };

  // just for the demo
  this.messages       = ko.observableArray([]);

  this.items          = ko.observableArray([]);
  this.json           = externalObservable;
  this.previous_json  = '';

  ko.computed(function() {
    var items = this.items(),
        json  = this.json();

    // If the JSON hasn't changed compared to the previous run,
    // that means we were called because an item was edited
    if (json === this.previous_json) {
      var new_json = ko.toJSON(items);

      self.messages.unshift("items were edited, updating JSON: " + new_json);

      this.previous_json = new_json;
      this.json(new_json);

      return;
    }

    // If we end up here, that means that the JSON has changed compared
    // to the last run

    self.messages.unshift("JSON has changed, updating items: " + json);

    var arrayOfObjects = JSON.parse(json),
        arrayOfObservables;

    // clear out everything, or otherwise we'll end
    // up with duplicated objects when we update
    this.items.removeAll();

    arrayOfObservables = ko.utils.arrayMap(arrayOfObjects, function(object) {
      return {
        text: ko.observable(object.text),
        value: ko.observable(object.value)
      };
    });

    // iterate over all observables in order
    // for our computed to get a subscription to them
    ko.utils.arrayForEach(arrayOfObservables, function(item) {
      item.text();
      item.value();
    });

    this.items(arrayOfObservables);

    this.previous_json = json;

  }, this);
}

var externalObservableFromParam = ko.observable(),
    viewModel;


// Pretend here that this observable was handed to us
// from your components' params
externalObservableFromParam('[{"value": "1", "text": "Low"}, {"value": "2", "text": "Medium"}, {"value": "3", "text": "High"} ]');

viewModel = new MyViewModel(externalObservableFromParam);

ko.applyBindings(viewModel);

＆＃13;

function MyViewModel(externalObservable) {
  var self = this;

  this.selectedItemSS = ko.observable();
  this.setSelectedSS  = function(item) {
    self.selectedItemSS(item);
  };
  
  // just for the demo
  this.messages       = ko.observableArray([]);

  this.items          = ko.observableArray([]);
  this.json           = externalObservable;
  this.previous_json  = '';
  
  ko.computed(function() {
    var items = this.items(),
        json  = this.json();
    
    // If the JSON hasn't changed compared to the previous run,
    // that means we were called because an item was edited
    if (json === this.previous_json) {
      var new_json = ko.toJSON(items);
      
      self.messages.unshift("items were edited, updating JSON: " + new_json);
      
      this.previous_json = new_json;
      this.json(new_json);
      
      return;
    }
    
    // If we end up here, that means that the JSON has changed compared
    // to the last run
    
    self.messages.unshift("JSON has changed, updating items: " + json);
    
    var arrayOfObjects = JSON.parse(json),
        arrayOfObservables;
    
    // clear out everything, or otherwise we'll end
    // up with duplicated objects when we update
    this.items.removeAll();

    arrayOfObservables = ko.utils.arrayMap(arrayOfObjects, function(object) {
      return {
        text: ko.observable(object.text),
        value: ko.observable(object.value)
      };
    });
    
    // iterate over all observables in order
    // for our computed to get a subscription to them
    ko.utils.arrayForEach(arrayOfObservables, function(item) {
      item.text();
      item.value();
    });

    this.items(arrayOfObservables);
    
    this.previous_json = json;

  }, this);
}

var externalObservableFromParam = ko.observable(),
    viewModel;


// Pretend here that this observable was handed to us
// from your components' params
externalObservableFromParam('[{"value": "1", "text": "Low"}, {"value": "2", "text": "Medium"}, {"value": "3", "text": "High"} ]');

viewModel = new MyViewModel(externalObservableFromParam);

ko.applyBindings(viewModel);

＆＃13;

body {
      font-family: arial;
      font-size: 14px;
    }
    .well {
      background-color: #eee;
      padding: 10px;
    }
    pre {
      white-space: pre-wrap;
    }
    ul {
      list-style-position: inside;
      }

＆＃13;

<script src="https://cdnjs.cloudflare.com/ajax/libs/knockout/3.2.0/knockout-min.js"></script>

<h3>Text Json: eg from AJAX request</h3>
<p>In practice this comes from a parent custom component as a parameter</p>
<pre class="well" data-bind="text: json"></pre>
<textarea data-bind="value: json" cols=50 rows=5></textarea>
<h3>Computed data model</h3>
<p>Click on an item to edit that record</p>
<div data-bind="foreach: items" class="well">
  <div data-bind="click: $parent.setSelectedSS">
    <span data-bind="text:value"></span>
    <span data-bind="text:text"></span>
    <br/>
  </div>
</div>

<hr/>

<h3>Editor</h3>
<div data-bind="with:selectedItemSS" class="well">
  <input data-bind="textInput:value" />
  <span data-bind="text:value"></span>
  <br/>
</div>

<hr/>

<h3>Console</h3>
<ul data-bind="foreach: messages" class="well">
  <li data-bind="text: $data"></li>
</ul>

＆＃13;

Knockout计算出observable不会触发'write'

1 个答案: