AngularJs替代ng-if以保存摘要 [英] AngularJs alternative to ng-if to save digest

问题描述

我最近开始研究AngulaJs的摘要和性能改进，并在我的网站上发现我正在使用大量的ng-if.

I recently started studying about digest and performance improvements in AngulaJs and found on my website that I'm using tons of ng-if.

有时在ng-if中有一个变量可能会更改，但通常在控制器启动时固定不变，然后永远不变.

Sometimes in ng-if there is a variable that may change, but often is fixed at the startup of the controller and then never changes.

我应该怎么做才能提高性能，避免摘要来评估每个不变的ng-if的每个循环?我应该更改指令吗?用什么?

What should I do so to improve performance avoiding digest to evaluate every loop those unchangeable ng-if? Should I change directive? With what?

例如

在标题模板中，我有一个div，只有特定类型的用户才能看到.它只是一个div，所以我不想调用其他模板. 我放了<div ng-if="userIsSuperior()"> ... </div>

In my header template I have a div that can be seen only by particular type of user. It's just a div, so I don't want to call some different template. I put <div ng-if="userIsSuperior()"> ... </div>

第一次评估时，userIsSuperior()的返回值从不改变(在本次课程中)，但是我知道AngularJs Digest会在每个循环中对其进行评估. 如何避免这种情况?还是我错过了什么?

When first evaluated, the return vale of userIsSuperior() never changes (during this session of course), but I know that AngularJs Digest evaluates it every loop. How can I avoid this? Or am I missing something?

推荐答案

我认为您正在寻找的是一次性绑定.

I think what you are looking for is one-time binding.

如果您使用:

<div ng-if="::userIsSuperior()"> ... </div>

然后userIsSuperior()的值将只计算一次，并保持该值不变.

Then the value of userIsSuperior() will only be calculated once and will stick to that value.

请参见演示.

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