AngularFire2 在 Array 中嵌套了 *ngFor Array...但 Firebase 没有数组...? [英] AngularFire2 nested *ngFor Array within Array... but Firebase doesn't have arrays...?

问题描述

我正在使用 AngularFire2，试图从列表中获取列表.*ngFor 中的嵌套 *ngFor 不会显示在视图中...

应用程序组件

<预><代码>...构造函数(私有_af:AngularFire){this.lists = this._af.database.list(this._API_URL);}...

app.component.html

{{sublist.name}}<br/><!-- 我能看见你--><!--******* 我看不见你 **********--><div *ngFor="let rootword of list.rootwords">{{rootword.word}} {{rootword.total}}

Firebase 示例

maindb|_list1||_name: '列表 1"||_词根||_苹果|||_word: '苹果'|||_总计:4||||_香蕉|||_word: '香蕉'|||_总计:2||_地毯|||_word: '地毯'|||_总计:21||_list2|_name: "列表 2"|_词根|_大象||_word: '大象'||_总计:4|_sloth|_word: '懒惰|_总计:5

如何将 ngFor 嵌套在带有 firebase.list 的 ngFor 中?我需要映射或过滤吗?AngularFire2 有办法把内部对象转成数组吗?

感谢所有建议！

解决方案

您可以使用 map 操作符 和 Array.prototype.reduce，像这样:

import 'rxjs/add/operator/map';构造函数(私有_af:AngularFire){this.lists = this._af.database.list(this._API_URL)//使用 map 操作符来替换列表中的每一项:.map(list => list.map(item => ({//映射到具有所有项目属性的新项目:...物品，//并用数组替换词根:词根:Object.keys(item.rootwords)//使用reduce来构建一个值数组:.reduce((acc, key) => [...acc, item.rootwords[key]], [])})));}

或者，没有展开语法:

import 'rxjs/add/operator/map';构造函数(私有_af:AngularFire){this.lists = this._af.database.list(this._API_URL).map(list => list.map(item => {var copy = Object.assign({}, item);copy.rootwords = Object.keys(item.rootwords).reduce((acc, key) => {acc.push(item.rootwords[key]);返回acc；}, []);返回副本；}));}

I'm using AngularFire2, trying to get lists out of lists. A nested *ngFor within an *ngFor doesn't show on the view...

app.componnent

...
constructor(private _af: AngularFire) {
    this.lists = this._af.database.list(this._API_URL);
}
...

app.component.html

<div *ngFor="let list of lists | async">
    {{sublist.name}}<br/> <!-- I can see you -->

    <!--******* I can't see you **********-->
    <div *ngFor="let rootword of list.rootwords">
        {{rootword.word}} {{rootword.total}}
    </div> 
</div>

Example of Firebase

maindb
  |_list1
  |  |_name: 'List 1"
  |  |_rootwords
  |     |_apple
  |     |   |_word: 'apple'
  |     |   |_total: 4
  |     |
  |     |_banana
  |     |   |_word: 'banana'
  |     |   |_total: 2
  |     |_carpet 
  |     |   |_word: 'carpet'
  |     |   |_total: 21
  |
  |_list2
     |_name: "List 2"
     |_rootwords
        |_elephant
        |    |_word: 'elephant'
        |    |_total: 4
        |_sloth
             |_word: 'sloth
             |_total: 5

How do you nest an ngFor in an ngFor with firebase.list ?? Do I need to map or filter? Does AngularFire2 have a way to convert the inner object to an array?

All suggestions appreciated!

解决方案

You can replace the rootwords object with an array using the map opererator and Array.prototype.reduce, like this:

import 'rxjs/add/operator/map';

constructor(private _af: AngularFire) {

  this.lists = this._af.database
    .list(this._API_URL)

    // Use map the map operator to replace each item in the list:

    .map(list => list.map(item => ({

      // Map to a new item with all of the item's properties:
      ...item,

      // And replace the rootwords with an array:
      rootwords: Object.keys(item.rootwords)

        // Use reduce to build an array of values:
        .reduce((acc, key) => [...acc, item.rootwords[key]], [])
      })
    ));
}

Or, without the spread syntax:

import 'rxjs/add/operator/map';

constructor(private _af: AngularFire) {

  this.lists = this._af.database
    .list(this._API_URL)
    .map(list => list.map(item => {
        var copy = Object.assign({}, item);
        copy.rootwords = Object.keys(item.rootwords).reduce((acc, key) => {
            acc.push(item.rootwords[key]);
            return acc;
        }, []);
        return copy;
    }));
}

这篇关于AngularFire2 在 Array 中嵌套了 *ngFor Array...但 Firebase 没有数组...?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！