两种方式绑定 Angularjs 指令不起作用

更新时间：2023-02-27 07:47:44

它更简单，所以我删除了你在那里的一些额外代码.

It's much simpler, so I have removed some extra code you had there.

请查看下面的代码或使用 Plunker:

Please take a look at the code below or working Plunker:

<!doctype html>
<html lang="en" ng-app="myApp">
    <head>
    <meta charset="UTF-8">
    <title>Document</title>
    <script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.0.8/angular.min.js"></script>

    <script>
        var myApp = angular.module('myApp', []);
        myApp.directive('postprocess', function ($timeout) {
            return {
                restrict : 'E',
                transclude: 'true',
                scope: {
                    myVariable: '='
                },
                link: function(scope, element, attrs) {
                    $timeout(function () {
                        scope.myVariable = 'Bye bye!'
                    }, 200);
                }  
            };
        });

        myApp.controller('myAppCtrl', ['$scope', '$timeout', function ($scope, $timeout) {
            $scope.myVariable = {
                value : 'Holla'
            };

            console.log($scope.myVariable.value); // -> prints initial value
            $timeout(function () {
                console.log($scope.myVariable.value); // -> prints value after it is changed by the directive
            }, 2000);
        }])
    </script>

    </head>
    <body ng-controller="myAppCtrl">
        <postprocess my-variable="myVariable.value" style="padding-top: 10px;" />
    </body>
</html>

控制器将初始值设置为Holla"
该指令通过 my-variable 属性接收该值
使用双向数据绑定对 scope.myVariable 所做的任何更改都会更新主控制器的 $scope.myVariable
几秒钟后 $scope.myVariable 更改为 'Bye Bye'
查看您的 console.log

The controller sets the initial value to 'Holla'
The directive receives that value by the my-variable attribute
Using two way data-binding any changes made to scope.myVariable updates the $scope.myVariable of the main controller
After few seconds $scope.myVariable changes to 'Bye Bye'
Take a look at your console.log

$watch 和 $apply

Angular 的双向数据绑定是 Angular 中所有 awesome 的根源.然而，这并不神奇，在某些情况下，您需要将其推向正确的方向.

Angular's two-way data binding is the root of all awesome in Angular. However, it's not magic, and there are some situations where you need to give it a nudge in the right direction.

当您使用 ng-model、ng-repeat 等将值绑定到 Angular 中的元素时，Angular 会在该值上创建一个 $watch.然后，每当作用域上的值发生变化时，所有观察该元素的 $watches 都会被执行，并且所有内容都会更新.

When you bind a value to an element in Angular using ng-model, ng-repeat, etc., Angular creates a $watch on that value. Then whenever a value on a scope changes, all $watches observing that element are executed, and everything updates.

有时，通常在您编写自定义指令时，您必须在范围值上定义自己的 $watch 以使指令对更改做出反应.

另一方面，有时您在某些代码中更改了范围值，但应用程序不会对其做出反应.在您的代码片段运行完毕后，Angular 检查范围变量的变化；例如，当 ng-click 调用作用域上的函数时，Angular 将检查更改并做出反应.但是，有些代码在 Angular 之外，您必须自己调用 scope.$apply() 来触发更新.这在自定义指令中的事件处理程序中最常见.

On the flip side, sometimes you change a scope value in some code but the app doesn't react to it. Angular checks for scope variable changes after pieces of your code have finished running; for example, when ng-click calls a function on your scope, Angular will check for changes and react. However, some code is outside of Angular and you'll have to call scope.$apply() yourself to trigger the update. This is most commonly seen in event handlers in custom directives.

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两种方式绑定 Angularjs 指令不起作用

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