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Two way binding Angularjs directives isn't working

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温柔的废话
温柔的废话 2020-12-30 09:01

I have been trying to figure out the solution but I think i hit a dead end.

So here is my directive

directive
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3条回答
  • 盖世英雄少女心
    2020-12-30 09:36

    be sure that you use the dot rule

    http://jimhoskins.com/2012/12/14/nested-scopes-in-angularjs.html

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  • 予麋鹿
    2020-12-30 09:40

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

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

    $watch and $apply

    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.

    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.

    Sometimes, usually when you're writing a custom directive, you will have to define your own $watch on a scope value to make the directive react to changes.

    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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  • 我在风中等你
    2020-12-30 09:52

    Some help from angularjs irc, & dluz, updated. Though I wish there was an easier way for the directive to be called, since the link function contains behavior and there should be a way to call that.

    http://jsfiddle.net/T7cqV/5/

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