默认情况下，Angular 中的 $scope.$$watchers 中添加了什么?什么触发了 $digests? [英] What gets added to $scope.$$watchers by default in Angular? And what triggers $digests?
问题描述
我正在阅读 构建您自己的 AngularJS 并且对如何$scopes, $watch 和 $digest 工作.我了解当您添加自己的 $watches 并调用自己的 $digests 时它是如何工作的.但是，我对默认情况下究竟发生了什么感到困惑.
I'm reading Build Your Own AngularJS and have a decent understanding of how $scopes, $watch and $digest work. I understand how it works when you add your own $watches and and call your own $digests. However, I'm confused about what exactly is happening by default.
默认情况下，
$scope.$$watchers会添加什么?你放在$scope上的所有东西?您为ng-model分配的所有内容?两个都?还有什么?
What gets added to
$scope.$$watchersby default? Everything you put on$scope? Everything you assign anng-modelto? Both? Something else?
$digests 什么时候被默认触发?输入字段更改?使用 ng-models 输入字段?其他?
And when exactly do $digests get triggered by default? Input field changes? Input fields with ng-models? Other?
推荐答案
一些使用 $watch/$watchCollection/$watchGroup<的常见指令/code> 内部:
Some of the common directives that use $watch / $watchCollection / $watchGroup internally:
- ng-model
- ng-bind/{{ }}
- ng-show &ng隐藏
- ng-class
- ng-repeat
- ng-if
- ng-switch
- ng-include
请注意，唯一设置双向绑定的是 ng-model (scope -> view & view -> scope).
Note that the only one that sets up a two-way binding is ng-model (scope -> view & view -> scope).
其他人设置了单向绑定(范围 -> 视图).
The others set up a one-way binding (scope -> view).
简单地在例如控制器的 $scope 上公开某些内容不会添加观察者.
Simply exposing something on for example a controller´s $scope will not add a watcher.
例如，以下不会导致添加观察者:
For example, the following will not result in a watcher being added:
angular.module('myApp', []).controller('Controller', function MyCtrl($scope) {
$scope.value = 1;
});
一起:
<body ng-app="myApp" ng-controller="Controller">
</body>
但是如果你用以下的 HTML 替换，将会添加一个观察者:
But if you replace the HTML with the following one watcher will be added:
<body ng-app="myApp" ng-controller="Controller">
<div>{{value}}</div>
</body>
<小时>
触发摘要循环时的一些常见场景:
Some common scenarios when the digest cycle is triggered:
- 当
ng-click被评估时 - 当
ng-model改变时(例如在输入时) - 通过
$http服务 - 在
$timeout和$interval
- When
ng-clickis evaluated - When
ng-modelchanges (for example when typing in an input) - By the
$httpservice - In
$timeoutand$interval
<小时>
请注意，$apply 和 $digest 之间有一个很大的区别:
Note that there is one big difference between $apply and $digest:
调用 scope.$digest() 将仅在该作用域及其子作用域上执行观察者.
Calling scope.$digest() will execute the watchers only on that scope and its children.
调用 scope.$apply() 将在 $rootScope 上触发 $digest，这意味着将遍历所有范围并且所有观察者被处决.
Calling scope.$apply() will trigger $digest on the $rootScope, which means all the scopes will be traversed and all watchers executed.
$apply 也接受一个表达式作为参数.该表达式将在 try-catch 语句中进行评估，任何异常都将传递给 $exceptionHandler 服务.
$apply also accepts an expression as an argument. This expression will be evaluated inside a try-catch statement and any exception will be passed on to the $exceptionHandler service.
$digest 不接受任何参数.
通常，当您追求微优化并且真正知道自己在做什么时，您只会调用 $digest 而不是 $apply.
Usually you only call $digest instead of $apply when you are chasing micro optimizations and really know what you are doing.
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