ng-switch 和 ng-repeat 对同一元素进行干扰 [英] ng-switch and ng-repeat on the same element interfearing

问题描述

我在 Angular 中遇到了我没想到的行为，这篇文章的目的是找出这是一个错误还是有意为之，并可能解释为什么要这样做.

I encountered behaviour in Angular I did not expect and the purpose of this post is to find out whether this is a bug or intended and possibly an explanation why it is intended.

首先看到这个Plunkr:http://plnkr.co/edit/CB7k9r?p=preview .在示例中，我创建了一个名为 array 的数组，其中包含三个对象条目.此外，我根据输入字段的内容(称为切换)创建了一个 ng-switch.当toggle的值为1时，它应该打印数组中以1"为前缀的所有对象名称，否则以other"为前缀.

First see this Plunkr: http://plnkr.co/edit/CB7k9r?p=preview . In the example I created an array called array with three object entries. Further I created a ng-switch based on the content of an input field (called toggle). When the value of toggle is 1 it should print all names of the objects in the array prefixed with "1" and otherwise prefixed with "other".

这不能正常工作并显示错误:

This does not work as intended an it shows an error:

Error: Argument '?' is required at assertArg 

然而，重写了相同的示例(http://plnkr.co/edit/68Mfux?p=preview ) 在列表周围有一个额外的 div，ng-switch 移动到这个 div，ng-switch-when 从 li 移动到 ul(将 ng-repeat 和 ng-switch-when 分开)确实按预期工作.

However the same example rewritten (http://plnkr.co/edit/68Mfux?p=preview ) with an extra div around the list, the ng-switch moved to this div and the ng-switch-when moved from the li to the ul (separating the ng-repeat and the ng-switch-when) does work as intended.

谁能解释一下这是为什么?

Could someone explain why this is?

推荐答案

这是有意的"，因为它是 angular 如何处理 ng-repeat 的产物.本质上，标记的多个副本被克隆(ng-repeat 中的标记用作模板)并为您正在迭代的每个元素单独编译.因此，angular 基本上是编译 3

和 3

，但这样做是脱离上下文的 - 没有可比较的 ng-switch-on 元素.

It is "intentional", as it is a product of how angular handles ng-repeat. Essentially, multiple copies of the markup are cloned (the markup inside ng-repeat is used as a template) and are compiled individually for each element you are iterating. As such, angular is basically compiling 3 <li ng-switch-when='1' ....> and 3 <li ng-switch-default ....>, but doing so out of context - there is no ng-switch-on element to compare to.

您可以通过检查生成的标记来看到这种情况:

You can see this happening by inspecting the resulting markup:

<ul ng-switch="" on="toggle">  
  <!-- ngRepeat: entry in array -->
  <!-- ngSwitchWhen: 1 -->
  <!-- ngSwitchWhen: 1 -->
  <!-- ngSwitchWhen: 1 -->
  <!-- ngRepeat: entry in array -->
  <!-- ngSwitchDefault:  -->
  <!-- ngSwitchDefault:  -->
  <!-- ngSwitchDefault:  -->        
</ul>

这两个指令 - ng-repeat 和 ng-switch - 都应该小心处理，因为它们(不像，例如，ng-show 或 ng-hide)严重影响结构.第二个(工作)Plunker 是要走的路 - 仅在(结构上，内部)ng-switch 逻辑之后使用指令.

Both directives - ng-repeat and ng-switch - should be handled with care, as they (unlike, for instance, ng-show or ng-hide) heavily influence structure. The second (working) Plunker is the way to go - only work with directives AFTER (structure-wise, INSIDE) the ng-switch logic.

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