Javascript Knockout.js - 如何在计算出的 observable 中获取 observable 属性的值？
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Knockout.js - how do I get the value of an observable property inside a computed observable?
提问by Arbejdsgl?de
I have following Knockout.js object:
我有以下 Knockout.js 对象：
var viewModel = {
description : ko.observable(""),
Name : ko.observable(""),
productid : ko.observable(""),
productmodel : ko.observable(""),
productnumber : ko.observable(""),
text_relevance : ko.observable(""),
mydunamicfield : ko.computed(function() {
return "bq=(and " +
((this.description == "") ? "" : ("description:" + this.description + " ")) +
")";
} , this)
};
But the mydunamicfieldproperty isn't producing the the correct concatenated result. If I try to reference this.description()inside another function, I see the following error message when the page is loading:
但是该mydunamicfield属性没有产生正确的连接结果。如果我尝试this.description()在另一个函数内部进行引用，则在加载页面时会看到以下错误消息：
Property 'description' of object [object Window] is not a function
What is the problem in this case?
在这种情况下有什么问题？
回答by Mark Robinson
Firstly, you must reference this.descriptionas this.description()if you want to get its value.
首先，您必须this.description像this.description()要获取其值一样进行引用。
Secondly, try putting your computedfield outside your viewModel(as 'this'which is the viewModelitself isn't defined at the point you create the computedobservable.
其次，可以尝试在你的computed领域你之外viewModel（因为'this'这是viewModel本身不是在点定义创建computed观测。
See http://jsfiddle.net/rAEqK/2/for a working example.
有关工作示例，请参阅http://jsfiddle.net/rAEqK/2/。
