剔除viewmodel属性未定义 [英] knockout viewmodel property undefined

问题描述

我有一个简单的foreach:

I have a simple foreach:

<div id="customersArea" data-bind="foreach: people">
            <div class="section" data-bind="attr: { 'personid': PersonId }" >
                <div class="sectionActions">
                    <div><a class="action" href="#" data-bind='click: $parent.removePerson'>Remove</a></div>
                </div>
                <div class="sectionText">
                    <span data-bind="if:LastName, text:LastName"></span>
                    <span data-bind="if:FirstName, text:FirstName"></span>
                    <span data-bind="if:MailingAddress">
                        <span data-bind="with:MailingAddress">
                            <span data-bind="text:StreetPartOne"> </span>
                            <span data-bind="text:StreetPartTwo">  </span>
                            <span data-bind="text:City"></span>
                            <span data-bind="text:PostalCode"></span>
                        </span>
                    </span>

                    <span data-bind="if:EmailAddress, text:EmailAddress"></span>
                    <span data-bind="if:MainPhoneNumber, text:MainPhoneNumber"></span>
                    <span data-bind="if:MobilePhoneNumber, text:MobilePhoneNumber"></span>

                </div>

                <div class="sectionOptions">

                </div>
            </div>
        </div>

我正在尝试使其能够与模型{PersonId:33}绑定，而其余的如果丢失就不会呈现.当我尝试这种方式和其他方式时

I am trying to make it such that i can bind against a model {PersonId:33} and the rest will just not render if missing. when i try it this and other ways i get

Uncaught Error: Unable to parse bindings.
Message: ReferenceError: MailingAddress is not defined;
Bindings value: if:MailingAddress

我创建了一个简单的jsfiddle进行测试:

I created a simple jsfiddle to test:

http://jsfiddle.net/E7kUr/

推荐答案

因此，您有一些选择:

当您尝试绑定未定义的属性时，

1. KO会出现问题，除非它们不在对象之外.因此，您可以在各种绑定之前加上$data.作为前缀，并且KO将能够解析您的绑定.示例: http://jsfiddle.net/rniemeyer/dLCL8/如果您知道总是会有几个属性在一起，则可以在这些选项周围使用with或if语句.

1. KO will have an issue when you try to bind against undefined properties, unless they are off of an object. So, you can prefix your various bindings with $data. and KO will be able to parse your bindings. Sample: http://jsfiddle.net/rniemeyer/dLCL8/ If you know that several properties will always be together, then you could use a with or if statement around those options.

处理未定义"属性的另一种方法是创建一个绑定，当缺少这些属性时，将填充这些属性.查看此答案.这将是相似的，但可能带有文本"绑定.样本: http://jsfiddle.net/rniemeyer/dLCL8/4/

A different take on handling "undefined" properties is to create a binding that populates these properties when they are missing. Look at this answer. It would be similar, but potentially with the 'text' binding. Sample: http://jsfiddle.net/rniemeyer/dLCL8/4/

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