聚合物1.0观察阵列

Question

I just tried to update my Polymer Website to version 1.0, but my array-observer-function does not work anymore. 我只是尝试将Polymer网站更新为1.0版，但是我的array-observer-function不再起作用。 So I had a look in the docs and noticed, that there is a new way to observe push & pop changes. 因此，我在文档中进行了查看，并注意到，有一种观察推送和弹出更改的新方法。

To test these changes, I copied the code from the Polymer docs , but even that example doesn't work... Here is my try to test the example script: 为了测试这些更改，我从Polymer docs复制了代码，但是即使该示例也不起作用...这是我尝试测试示例脚本的方法：

<!doctype html>
<html>
<head>
  <title>Test</title>
    <meta name="viewport" content="width=device-width, minimum-scale=1.0, initial-scale=1.0, user-scalable=yes"> 
    <script src="/bower_components/webcomponentsjs/webcomponents-lite.min.js"></script>
    <link rel="import" href="/bower_components/polymer/polymer.html">
    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
</head>
<body>
    <my-index></my-index>
</body>
</html>
<dom-module id="my-index">
<script>
    Polymer({
        is: "my-index",
        properties: {
            users: {
                type: Array,
                value: function() {
                    return [];
                }
            }
        },

        observers: [
            'usersAddedOrRemoved(users.splices)'
        ],
        ready: function(){
            this.addUser();
        },
        usersAddedOrRemoved: function(changeRecord) {
            console.log(changeRecord);
            changeRecord.indexSplices.forEach(function(s) {
                s.removed.forEach(function(user) {
                    console.log(user.name + ' was removed');
                });
                console.log(s.addedCount + ' users were added');
            }, this);
        },

        addUser: function() {
            this.push('users', {name: "Jack Aubrey"});
        }
  });
</script>
</dom-module>

The javascript-console just says Uncaught TypeError: Cannot read property 'indexSplices' of undefined . javascript控制台仅显示Uncaught TypeError: Cannot read property 'indexSplices' of undefined 。 Any ideas what is wrong? 任何想法有什么问题吗？

Answer 1

The usersAddedOrRemoved function is firing at the start when the users array is created (with an undefined changeRecord). 创建users数组时（带有未定义的changeRecord），在开始时会触发userwegoOrRemoved函数。 If you handle the undefined you'll see it works as expected and fires both at the start and on the user added. 如果您处理未定义的内容，您会看到它可以按预期工作，并且会在开始时和添加的用户上触发。

usersAddedOrRemoved: function(changeRecord) {
        console.log(changeRecord);
        if (changeRecord) {
            changeRecord.indexSplices.forEach(function(s) {
                s.removed.forEach(function(user) {
                    console.log(user.name + ' was removed');
                });
                console.log(s.addedCount + ' users were added');
            }, this);
        }
    },

聚合物1.0观察阵列

问题描述

1 个解决方案

解决方案1
1 已采纳 2015-06-24 10:06:16

聚合物1.0观察阵列

问题描述

1 个解决方案

解决方案1 1 已采纳 2015-06-24 10:06:16

解决方案1
1 已采纳 2015-06-24 10:06:16