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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