角$范围。$适用VS $超时作为一个安全的应用$ [英] Angular $scope.$apply vs $timeout as a safe $apply

问题描述

我想更好地理解角度使用$超时服务作为一种安全$适用法的细微差别。基本上在一块code都可以根据到任何一个角度的事件或作为jQuery的或者一些标准的DOM事件无棱角事件，例如运行场景。

据我了解的事情：

1. 包装code $中的范围。$申请精品工程的情况下，您
   是不是已经在消化循环（亦称jQ​​uery的事件），但如果一个消化过程中会产生一个错误


2. 包装code在$超时（）调用无延迟参数是否工作已处于消化周期或不

综观角源$ C ​​$ C，它看起来像$超时使得至$ rootScope的调用。$适用（）。

1. 为什么不$超时（）也如摘要周期正在进行中引发错误？


2. 就是用$范围内的最佳实践。$适用（）的时候，你肯定知道摘要不会已经在进步和$超时（）需要它的时候是安全的无论哪种方式？


3. 为$超时（）真的可以接受的安全应用，还是有陷阱？

感谢您的任何见解。

解决方案

  

综观角源$ C ​​$ C，它看起来像$超时使一个呼叫
  $ rootScope。$适用（）。

  
  

  
• 为什么不$超时（）也如摘要周期正在进行中引发错误？

  

$超时利用无证角服务 $浏览器。具体来说，它使用 $ browser.defer（）异步通过 window.setTimeout（FN，延迟），这将永远运行的角度生命周期之外。只有当 window.setTimeout 已触发你的函数将 $超时通话 $ rootScope。$申请（）。

  

  
• 就是用$范围内的最佳实践。$适用（）的时候，你肯定知道摘要不会已经在进步和$超时（）需要它的时候是安全的无论哪种方式？

  

我会这么说。另一个用例是，有时你需要访问你只知道将消化后初始化$范围的变量。如果你想设置你的控制器构造（无论何种原因）内的表单的状态脏简单的例子是。如果没有$超时的FormController 尚未初始化并公布到$范围，所以包装 $ scope.yourform.setDirty（）在$超时确保的FormController 已初始化。当然，你可以做到这一切有没有指令$超时，只是给另一使用情况实例。

  

  
• 为$超时（）真的可以接受的安全应用，还是有陷阱？

  

它应该永远是安全的，但你转到方法应始终瞄准$适用（）在我看来。当前角度应用我的工作是相当大，我们只有依靠$超时一次，而不是$适用（）。

I'm trying to better understand the nuances of using the $timeout service in Angular as a sort of "safe $apply" method. Basically in scenarios where a piece of code could run in response to either an Angular event or a non-angular event such as jQuery or some standard DOM event.

As I understand things:

1. Wrapping code in $scope.$apply works fine for scenarios where you aren't already in a digest loop (aka. jQuery event) but will raise an error if a digest is in progress
2. Wrapping code in a $timeout() call with no delay parameter works whether already in a digest cycle or not

Looking at Angular source code, it looks like $timeout makes a call to $rootScope.$apply().

1. Why doesn't $timeout() also raise an error if a digest cycle is already in progress?
2. Is the best practice to use $scope.$apply() when you know for sure that a digest won't already be in progress and $timeout() when needing it to be safe either way?
3. Is $timeout() really an acceptable "safe apply", or are there gotchas?

Thanks for any insight.

解决方案

Looking at Angular source code, it looks like $timeout makes a call to $rootScope.$apply().

• Why doesn't $timeout() also raise an error if a digest cycle is already in progress?

$timeout makes use of an undocumented Angular service $browser. Specifically it uses $browser.defer() that defers execution of your function asynchronously via window.setTimeout(fn, delay), which will always run outside of Angular life-cycle. Only once window.setTimeout has fired your function will $timeout call $rootScope.$apply().

• Is the best practice to use $scope.$apply() when you know for sure that a digest won't already be in progress and $timeout() when needing it to be safe either way?

I would say so. Another use case is that sometimes you need to access a $scope variable that you know will only be initialized after digest. Simple example would be if you want to set a form's state to dirty inside your controller constructor (for whatever reason). Without $timeout the FormController has not been initialized and published onto $scope, so wrapping $scope.yourform.setDirty() inside $timeout ensures that FormController has been initialized. Sure you can do all this with a directive without $timeout, just giving another use case example.

• Is $timeout() really an acceptable "safe apply", or are there gotchas?

It should always be safe, but your go to method should always aim for $apply() in my opinion. The current Angular app I'm working on is fairly large and we've only had to rely on $timeout once instead of $apply().

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