使用来自* ngFor以外的数据* ngFor范围

Question

以下是我想要实际解决的示例问题。你的帮助将非常感激。非常感谢！

<div> 
    <div> 
    <!-- is it possible to put the item.preview here? 
     It is outside of *ngFor 
    --> 
    </div> 
    <div *ngFor="let item of items"> 
     <img [src]="item.cover" alt="item.name"> 
    </div> 
</div> 

Answer 1

---

没有办法直接显示的* ngFor之外的一个项目，除非你设置的项目到变量之一。通常这将基于某些事件（例如点击（），鼠标悬停（）等）。

下面是一个示例，显示了用户单击图像时的常见模式，这设置了另一个变量，然后显示在任何地方根据需要在组件上进行其他操作

这里是一个工作plunker： https://plnkr.co/edit/TzBjhisaPCD2pznb10B0?p=preview

import {Component, NgModule, VERSION, OnInit, Input} from '@angular/core' 
import {BrowserModule} from '@angular/platform-browser' 

interface Item { 
    id: number; 
    name: string; 
    covor: string 
} 

@Component({ 
    selector: 'my-app', 
    template: ` 
    <div> 
     <h2>Hello {{name}}</h2> 
    </div> 
    <div> 
    <div> 
     {{selectedItem | json}} 
    </div> 
    <div *ngFor="let item of items"> 
     <img [src]="item.cover" alt="item.name" (click)="selectItem(item)"> 
    </div> 
    </div> 
    `, 
}) 
export class App implements OnInit { 
    name:string; 

    // This is an input just to show that this might be where the data comes from 
    // otherwise call a service to set the data initially 
    @Input() items: Item[] = [ 
    {id: 1, name: 'test', cover: 'https://i.vimeocdn.com/portrait/58832_300x300'}, 
    {id: 2, name: 'test2', cover: 'https://lh4.ggpht.com/wKrDLLmmxjfRG2-E-k5L5BUuHWpCOe4lWRF7oVs1Gzdn5e5yvr8fj-ORTlBF43U47yI=w300'}, 
    ]; 
    selectedItem: Item; 

    constructor() { 
    this.name = `Angular! v${VERSION.full}` 
    } 

    ngOnInit() { 
    // you can init your item here 
    if(this.items.length > 0) { 
     this.selectedItem = this.items[0]; 
    } 
    } 

    selectItem(item: Item) { 
    this.selectedItem = item; 
    } 
} 

@NgModule({ 
    imports: [ BrowserModule ], 
    declarations: [ App ], 
    bootstrap: [ App ] 
}) 
export class AppModule {}