以$手表VS NG-变化，NG-检查等角度触发的变化

问题描述

目前，我们可以监督几个方面的数据变化。我们可能会引发与 $模式的变化看键，我们可以添加指令，以元素并结合了一些行动吧。

Currently we could monitor data changes with several ways. We could trigger model changes with $watch and we could add directives to elements and bind some actions to it.

这是在很多情况下，稍微有点混乱，所以我很好奇，这是亲和每个变量的利弊，我们何时应该使用 $观看绑定，当指令就像 NG-变化？

It's a little bit confusing in many cases, so I'm curious, which is pro and cons of each variant and when should we use $watch binding, and when directives like ng-change?

推荐答案

两个 $观看和 ngChange 有完全不同的用途：

Both $watch and ngChange have totally different usages:

假设你有一个范围内定义的模型：

Lets say you have a model defined on a scope:

$scope.myModel = [
    {
        "foo":"bar"
    }
];

基于myModel 你可以使用 $观看的东西

现在p>

Now if you want to do something whenever any changes happen to myModel you would use $watch:

$scope.$watch("myModel", function(newValue, oldValue){
    // do something
});

ngChange 是将评估给出前pression指令，当用户改变输入：

ngChange is a directive that would evaluate given expression when user changes the input:

<select ng-model="selectedOption" ng-options="option for option in options" 
ng-change="myModel=selectedOption"></select>

总之，你通常会绑定 ngChange 来一些HTML元素。而 $观看是模型。

In short, you would normally bind ngChange to some HTML element. While $watch is for the models.

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