Polymer 1.0 观察阵列

Question

我刚刚尝试将我的 Polymer 网站更新到 1.0 版，但我的数组观察器功能不再起作用。所以我查看了文档并注意到，有一种观察推送和弹出更改的新方法。

为了测试这些更改，我从 Polymer docs 复制了代码，但即使是那个示例也不起作用...这是我测试示例脚本的尝试：

<!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>

javascript-控制台只显示 Uncaught TypeError: Cannot read property 'indexSplices' of undefined。有什么想法吗？

Answer 1

usersAddedOrRemoved 函数在创建 users 数组时触发（使用未定义的 changeRecord）。如果你处理未定义的，你会看到它按预期工作，并在开始时和添加的用户时触发。

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);
        }
    },

Polymer 1.0 观察阵列

Polymer 1.0 Observe Array

javascript

html

polymer-1.0