observable不更新自定義綁定

請參閱附加的代碼。observable不更新自定義綁定

DummyText是可觀察的並且在ko.bindingHandlers.dummytext中定義了自定義綁定。但是，this.DummyText("dummy_text_" + this.firstName());僅調用update: function (element, valueAccessor,....一次，因此<span data-bind="dummytext: DummyText"></span>僅更新一次。

創建文本作爲文本綁定的引用，並且始終更新<span data-bind="text: Text"></span>。

如何讓this.DummyText("dummy_text_" + this.firstName());隨時撥打update: function (element, valueAccessor,....

<html> 
<head> 
</head> 
    <script src="//ajax.aspnetcdn.com/ajax/jQuery/jquery-1.9.1.js"></script> 
    <script src="//ajax.aspnetcdn.com/ajax/knockout/knockout-2.2.1.debug.js"></script> 
<body> 
    <p>First name: <input data-bind="value: firstName" /></p> 
    <p>Last name: <input data-bind="value: lastName" /></p> 
    <h2>Hello, <span data-bind="text: fullName"> </span>!</h2> 
    <div><span data-bind="text: Text"></span></div> 
    <div><span data-bind="dummytext: DummyText"></span></div> 

    <script> 
     ko.bindingHandlers.dummytext = { 
      //init: function (element, valueAccessor, allBindingsAccessor, viewModel, bindingContext) { 
      //}, 
      update: function (element, valueAccessor, allBindingsAccessor, viewModel, bindingContext) { 
       var value = valueAccessor(), allBindings = allBindingsAccessor(); 
       var s = value._latestValue; 
       $(element).html(s); 
      } 
     }; 

     var ViewModel = function (first, last) { 
      this.firstName = ko.observable(first); 
      this.lastName = last; 
      this.DummyText = ko.observable("dummy_text_"); 
      this.Text = ko.observable("text_"); 

      this.fullName = ko.computed(function() { 
       this.Text("text_" + this.firstName()); 
       this.DummyText("dummy_text_" + this.firstName()); 

       return this.firstName() + " " + this.lastName; 
      }, this); 
     }; 

     ko.applyBindings(new ViewModel("Planet", "Earth")); 
     </script> 

</body> 
</html>

來源

2013-08-21 Giant Jupiter

您應該使用值（）而不是value._latestValue觸發依賴關係，基因敲除能知道當值被更新當前綁定需要刷新：

看看這個：http://jsfiddle.net/b4bDQ/

ko.bindingHandlers.dummytext = { 
     //init: function (element, valueAccessor, allBindingsAccessor, viewModel, bindingContext) { 
     //}, 
     update: function (element, valueAccessor, allBindingsAccessor, viewModel, bindingContext) { 
      var value = valueAccessor(), allBindings = allBindingsAccessor(); 
      var s = value(); // Here should use() to trigger the subcribing dependency // value._latestValue; 
      $(element).html(s); 
     } 
    };

來源

2013-08-21 19:01:21

是的，你應該永遠不會需要使用'__latestValue'直接 - 除非，也許，你正在寫一個淘汰賽插件...即使這樣，我會盡可能避免它。 –

是的，你是對的。 value（）（1）註冊依賴關係，以便再次調用update（），（2）返回__latestValue。 –

observable不更新自定義綁定

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