在Angular的控制器之间共享数据，观看还是不观看？

Question

I read the following questions and answers: Share data between AngularJS controllers , Update scope value when service data is changed , and Angular: Update service and share data between controllers . 我阅读了以下问题和解答：在AngularJS控制器之间共享数据，在更改服务数据时更新范围值，以及Angular：在控制器之间更新服务并共享数据。

My question is about the answers provided. 我的问题是关于提供的答案。 The answers often suggest to $watch and I don't understand why. 答案通常暗示$watch ，但我不明白为什么。

I wanted to share some values between controllers so I simply did this (this is a simplification of the code): 我想在控制器之间共享一些值，所以我简单地做到了这一点（这是代码的简化）：

  angular.module('app', [])
.factory('SomeSharedData', function() 
{
  return { 'pointer' : { 'someKey' : 'someValue' }};
})

.controller('Controller1', ['$scope', 'SomeSharedData', function($scope, SomeSharedData) {
  $scope.pointer = SomeSharedData.pointer;
}])

.controller('Controller2', ['$scope', 'SomeSharedData', function($scope, SomeSharedData)
{
  $scope.pointer = SomeSharedData.pointer;
}]);

Is this inheritly evil for some reason? 这是出于某种原因而继承的邪恶吗？

Why use something like: 为什么要使用类似：

$scope.$watch(function () { return SomeSharedData.someKey(); }, function (newValue) {
    if (newValue) $scope.someKey = newValue;
});

Answer 1

It actually depends, in your case the pointer variable in the controller will be set to the SomeSharedData factory pointer variable. 实际上取决于您的情况，控制器中的指针变量将设置为SomeSharedData工厂指针变量。 So there is no need to use $watch in your case as the variable will be set once. 因此，在您的情况下无需使用$ watch，因为变量将被设置一次。

But, what if you want to do something if the pointer variable in the controller changes. 但是，如果控制器中的指针变量发生更改，您想做些什么，该怎么办？ You will not know, whether the pointer variable has changed if you don't use $watch (that is what the $watch is for). 您将不知道，如果不使用$ watch（这就是$ watch的目的），则指针变量是否已更改。

Like, take an example. 像，举个例子。 Here i have created a model called pointer and i am watching for changes, and if anything changes the count is increased by 1 everytime. 在这里，我创建了一个称为指针的模型，我正在监视更改，如果发生任何更改，则每次计数都会增加1。 In this case the $watch is necessary. 在这种情况下，需要$ watch。 So, if in any case you want to do something if the model is changes, you can use $watch. 因此，如果在任何情况下您都想更改模型，则可以使用$ watch。

index.html 的index.html

<!doctype html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Angular $watch</title>
    <script src="//ajax.googleapis.com/ajax/libs/angularjs/1.2.25/angular.min.js"></script>

</head>
<body>
<div ng-app="myApp">
    <div ng-controller="myCtrl">
        <input type="text" ng-model="pointer">
        {{pointer}}
        <br>
        <h3>Will increase if input changes:<h1>{{count}}</h1></h3>  
    </div>
</div>           

    <script src="main.js"></script>
</body>
</html>

main.js main.js

var myApp = angular.module('myApp', []);

myApp.controller('myCtrl', ['$scope', function ($scope) {
    $scope.count = 1;
    $scope.$watch('pointer', function(newValue, oldValue) {
        if ( newValue !== oldValue ) {
            $scope.count += 1;
        }        
    });
}]);

在Angular的控制器之间共享数据，观看还是不观看？

问题描述

1 个解决方案

解决方案1
1 已采纳 2014-09-21 16:14:18

在Angular的控制器之间共享数据，观看还是不观看？

问题描述

1 个解决方案

解决方案1 1 已采纳 2014-09-21 16:14:18

解决方案1
1 已采纳 2014-09-21 16:14:18