为什么在单元测试中的$ compile（element）（范围）之后调用scope。$ digest（） [英] Why call scope.$digest() after $compile(element)(scope) in unit testing

问题描述

以下是用于测试指令的非常常见的通用场景：

Below is a very common generic scenario used for testing directive:

var element,scope;

beforeEach(inject(function ($rootScope,$compile) {
  scope = $rootScope.$new()
  element = angular.element('<div my-directive></div>')
  $compile(element)(scope)
  scope.$digest(); //why?
}))

我理解 $ compile（element）返回一个带有范围参数的函数并将其提供给元素的指令。我也明白范围。$ digest（）执行摘要循环并开始脏检查。尽管如此，我的问题是为什么你必须在调用 $ compile 之后调用范围。$ digest 一切都适用于这种情况？

I understand $compile(element) returns a function that take a scope parameter and provides it to the element's directive. I also understand that scope.$digest() executes the digest loop and start dirty-checking. With all that said, my question is why you have to call the scope.$digest after calling $compile to make everything works in this situation?

推荐答案

这是用于测试指令的通用代码。 $ Compile 使用范围绑定模板并执行 link 函数和 $ digest / $ apply 刷新可能已被链接修改的模型的绑定。

当您在 ng-click 处理程序或控制器函数中调用 $ compile 时，整个执行将在<$内部运行c $ c> $ digest 循环。 Angular以这样的方式构建，即动态添加的项（在执行此循环时）在同一循环中执行。这就是为什么你实际上没有注意到差异，并且没有意识到编译后需要绑定评估。然而，它在单元测试中有所不同，你应该告诉angular手动执行 $ digest 循环。例如，在测试 $ q 承诺时，这通常会导致问题。

This is a generic code for testing a directive. $Compile binds template with scope and executes link function and $digest/$apply refreshes bindings for models that might have been modified by link.
When you call $compile inside ng-click handler or in controller function, the whole execution is run inside a $digest loop. Angular is built in such a way that dynamically added items (while executing this loop) are executed in same cycle. That is why you don't actually notice the difference and don't realize the need for binding evaluations after compilation. However it's way different in unit tests, where you should tell angular to execute a $digest cycle manually. This often results in problems when testing $q promises, for example.

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