Polymer 1.x: Deleting an item from iron-list

问题

I am trying to delete an item from iron-list using the following code.

my-element.html

<iron-list id="list" items="[[items]]" as="item"
           selected-items="{{selectedItems}}"
           selection-enabled multi-selection>
  <template>
    <my-item item="[[item]]" on-tap="_onItemTap"></my-item>
  </template>
</iron-list>
...
_onItemTap: function(e) {
  this.items.splice(e.model.index, 1);
}

Expected behavior

Tap list item
List item disappears
Select next list item
Next list item is selected

Actual behavior

Tap list item
List item does not disappear
Select same list item (i.e., the one previously intended to be deleted)
Next list item is actually selected (i.e., index offset by one)

Questions

What code will result in the desired / expected behavior?
Please provide a working jsBin sample.

回答1:

See this answer for specific syntax contributing to the problem.

Here is a working JSBin.

http://jsbin.com/qefemoloxi/1/edit?html,console,output

<!doctype html>
<head>
  <meta charset="utf-8">
  <base href="https://polygit.org/components/">
  <script src="webcomponentsjs/webcomponents-lite.min.js"></script>
  <link href="polymer/polymer.html" rel="import">
  <link href="paper-button/paper-button.html" rel="import">
  <link href="iron-list/iron-list.html" rel="import">
</head>
<body>

<dom-module id="x-element">

<template>
  <style>
    iron-list {
      height: 100vh;
    }
  </style>
  <iron-list id="list" items="[[items]]" as="item">
    <template>
      <paper-button on-tap="_deleteItem">[[item.name]]</paper-button>
    </template>
  </iron-list>
</template>

<script>
  (function(){
    Polymer({
      is: "x-element",
      properties: {
        items: {
          type: Array,
          value: function() {
            return [
              { 'name':'foo' },
              { 'name':'bar' },
              { 'name':'qux' },
              { 'name':'baz' },
              { 'name':'quux'}
            ]
          }
        }
      },
      _deleteItem: function(e) {
        console.log(e.model.index);
        this.splice('items', e.model.index, 1);
        this.$.list.fire('resize');
      }
    });
  })();
</script>

</dom-module>

<x-element></x-element>

</body>

回答2:

A summary of this page suggests this documentation as follows:

Question

app.removeItem = function(index) {
  app.data.splice(index, 1);
  console.log("Removing " + index);
  document.querySelector('#tobuy').fire('resize');
};

document.querySelector('#tobuy').push('items', {name: "Foo"})

then you don't need to call resize.

ref: https://www.polymer-project.org/1.0/docs/devguide/properties.html#array-observation

回答3:

This documentation on array mutation provides the following boilerplate code:

custom-element.html

<dom-module id="custom-element">
  <template>
    <template is="dom-repeat"></template>
  </template>
  <script>
    Polymer({
      is: 'custom-element',
      addUser: function(user) {
        this.push('users', user);
      },
      removeUser: function(user) {
        var index = this.users.indexOf(user);
        this.splice('users', index, 1);
      }
    });
  </script>
</dom-module>

Applying that to this case:

my-element.html

// As a syntactical matter, replace the following line
// this.items.splice(e.model.index, 1);
// With this line
this.splice('items', e.model.index, 1);
this.$.list.fire('resize');

A problem with this solution, however, is that it deletes the last item from the iron-list, not the item at the expected index. In other words, it behaves like one would expect this.items.pop().

It also throws the following curious error message:

console.log

Uncaught TypeError: <item> should be a valid item

回答4:

See this answer for full code solution.

The problem here was caused by the fact that my item.html file was setting and displaying properties outside the item. property. So, when the iron-list.(this.)splice('items', e.model.index, 1); array mutation method was called, the non item properties were not being removed from the DOM.

Example:

my-list-item.html

this.set(     'name', this.item.foo.bar.qux); // This syntax caused the problem
this.set('item.name', this.item.foo.bar.qux); // This fixed the problem

my-iron-list.html

this.splice('items', e.model.index, 1);

来源：https://stackoverflow.com/questions/34627793/polymer-1-x-deleting-an-item-from-iron-list

标签

polymer

polymer-1.0