保持“$ watch”功能远离控制器的最佳做法 [英] Best practice in keeping `$watch` functions away from your controllers

问题描述

我试图找到一些关于将 $ watch 函数从控制器移动到工厂的最佳实践的好例子。例如。

I tried to find some good examples on best practice in moving $watch functions from a controller to a factory, for example.

我发现的是，实际上对于什么是最好的做法没有一致意见。我已经看到了将 $ rootScope 注入工厂的示例以及 $ watch ，以便在那里进行值更改。

What I have found is that actually there isn't a unanimous opinion on what's best to do. I've seen examples of injection the $rootScope into a factory and $watching for value changes there.

另一个建议是尽可能避免使用它们，并在元素本身上使用 ngChange ，例如：

Another suggestion is to avoid them whenever possible, and to use ngChange instead on the element itself, for example:

<div ng-model="foo.bar" ng-change="updateValue(foo.bar)"></div>

您建议的方式是什么？自从我开始学习AngularJS以来，我一直在我的控制器中放置 $ watch es，但现在我想采用最佳实践方法，尝试制作并保持我的控制器像可能。

What is your proposed way? I've been putting $watches in my controllers ever since I started learning AngularJS but now I want to embrace best practice approaches, trying to make and keep my controllers as thin as possible.

推荐答案

我想放在哪里 $ watch 在很大程度上取决于用例场景。关于 $ watch 最重要的一点是不要在句柄功能中做任何艰苦的工作，特别是如果你正在观看的内容正在发生很大变化;这会严重阻碍你的表现。并确保在您的句柄功能中您不会更改已经被观看的其他内容，因为这将导致更改链更新。

I guess where to put $watch heavily depends on the use-case scenario. The most important thing to be careful about $watch is not to do any hard-work inside the handle function especially if what you are watching is changing a lot; that would highly damper your performance. And be sure that in your handle function you don't change something else which is already being watched as this will cause a chain of change updates.

如果您确定您正在观看的变量只能在一个地方更改，最好使用 ng-change 而不是 $ watch 因为你已经知道它被改变的地方。

If you are sure that the variable you are watching can only be changed from one place, it is better idea to use ng-change rather than $watch as you already know the place where it gets changed.

一般来说，最好不要填写 rootScope 使用不必要的对象，但是如果你正在观察整个应用程序中使用的某些变量，例如当前用户的属性，我想将 $ watch 表达式放入 $ rootScope 。

It is generally good practice not to fill rootScope with unnecessary objects, but if you are watching for some variable which is used in entire application such as current user's attribute, I guess it would make sense to put $watch expression into $rootScope.

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