AngularJS 模板中的 if else 语句 [英] if else statement in AngularJS templates

问题描述

我想在 AngularJS 模板中做一个条件.我从 Youtube API 获取视频列表.部分视频的比例为 16:9，部分视频的比例为 4:3.

我想创建一个这样的条件:

如果 video.yt$aspectRatio 等于宽屏，则元素的属性 height="270px"别的元素的属性 height="360px"

我正在使用 ng-repeat 迭代视频.不知道我该怎么办这种情况:

• 在作用域中添加函数?
• 在模板中做吗?

解决方案

Angularjs(低于 1.1.5 的版本)不提供 if/else 功能.以下是您要实现的目标，需要考虑的几个选项:

(如果您使用的是 1.1.5 或更高版本，请跳转到下面的更新 (#5))

1.三元运算符:

正如@Kirk 在评论中所建议的，最简洁的方法是使用三元运算符，如下所示:

{{isLarge ?'video.large' : 'video.small'}}</span>

2.ng-switch 指令:

可以像下面这样使用.

<div ng-switch-when="video.large"><!-- 渲染大视频块的代码-->
<div ng-switch-default><!-- 呈现常规视频块的代码-->

3.ng-hide/ng-show 指令

或者，您也可以使用 ng-show/ng-hide 但使用它实际上会同时渲染一个大视频和一个小视频元素，然后隐藏符合 ng 的元素-hide 条件并显示符合ng-show 条件的那个.因此，在每个页面上，您实际上将呈现两个不同的元素.

4.另一个需要考虑的选项是 ng-class 指令.

这可以如下使用.

<!-- 视频块放在这里-->

如果 video.large 为真的话，上面基本上会向 div 元素添加一个 large-video css 类.

更新:Angular 1.1.5 引入了 ngIf 指令

5.ng-if 指令:

在 1.1.5 以上的版本中，您可以使用 ng-if 指令.如果提供的表达式返回 false，这将删除元素，如果表达式返回 true，则将 element 重新插入 DOM.可以如下使用.

<!-- 渲染大视频块的代码-->
<div ng-if="video != video.large"><!-- 呈现常规视频块的代码-->

I want to do a condition in an AngularJS template. I fetch a video list from the Youtube API. Some of the videos are in 16:9 ratio and some are in 4:3 ratio.

I want to make a condition like this:

if video.yt$aspectRatio equals widescreen then 
    element's attr height="270px"
else
    element's attr height="360px"

I'm iterating the videos using ng-repeat. Have no idea what should I do for this condition:

• Add a function in the scope?
• Do it in template?

解决方案

Angularjs (versions below 1.1.5) does not provide the if/else functionality . Following are a few options to consider for what you want to achieve:

(Jump to the update below (#5) if you are using version 1.1.5 or greater)

1. Ternary operator:

As suggested by @Kirk in the comments, the cleanest way of doing this would be to use a ternary operator as follows:

<span>{{isLarge ? 'video.large' : 'video.small'}}</span>

2. ng-switch directive:

can be used something like the following.

<div ng-switch on="video">
    <div ng-switch-when="video.large">
        <!-- code to render a large video block-->
    </div>
    <div ng-switch-default>
        <!-- code to render the regular video block -->
    </div>
</div>

3. ng-hide / ng-show directives

Alternatively, you might also use ng-show/ng-hide but using this will actually render both a large video and a small video element and then hide the one that meets the ng-hide condition and shows the one that meets ng-show condition. So on each page you'll actually be rendering two different elements.

4. Another option to consider is ng-class directive.

This can be used as follows.

<div ng-class="{large-video: video.large}">
    <!-- video block goes here -->
</div>

The above basically will add a large-video css class to the div element if video.large is truthy.

UPDATE: Angular 1.1.5 introduced the ngIf directive

5. ng-if directive:

In the versions above 1.1.5 you can use the ng-if directive. This would remove the element if the expression provided returns false and re-inserts the element in the DOM if the expression returns true. Can be used as follows.

<div ng-if="video == video.large">
    <!-- code to render a large video block-->
</div>
<div ng-if="video != video.large">
    <!-- code to render the regular video block -->
</div>

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