角度-对象作为选择选项值 [英] Angular - Objects as Select Option Values

问题描述

我有一个带有各种选择框的表单，这些选择框使用对象作为值:

I have a form with various select boxes which use objects as the value:

< mat-option [value] ="object">

当我通过表单创建新记录时，哪一个工作得很好?现在，当我编辑记录时，遇到了一个问题，即 mat-select-option 中的 object 不是我从休息服务中获得的相同"对象，因此在编辑记录时我的选择框没有选择任何选项.

Which works great when I am creating new records via the form. Now when I am editing records, I run into the problem that the object in the mat-select-option is not the "same" object that I get from my rest service, so my select boxes have no option selected when editing the record.

在决定选择哪个选项时，是否可以告诉选择框窗口小部件在 object.id 上匹配?我想我可能需要编写一条指令来处理此问题，但是对于Angular或Angular Material库或其他现有解决方案，这可能已经成为可能.

Is it possible to tell the select-box widget to match on object.id when deciding what option is selected? I think I may need to write a directive to handle this, but maybe this is already possible with Angular or Angular Material libraries, or another existing solution.

为了详细说明，我有我的 foo.component.ts 文件:

To elaborate I have my foo.component.ts file:

let item = {
    'fruit': { id: 1, 'label': 'Pineapple' },
}

let options = [
    { 'id':1, 'label': 'Pineapple' },
    { 'id':2, 'label': 'Banana' },
    { 'id':3, 'label': 'Papaya' }
]

和我的 .html 文件:

<mat-select  placeholder="Fruit" [(ngModel)]="item.fruit">
  <mat-option *ngFor="let option of options" [value]="option">{{option.label}}</mat-option>
</mat-select>

当用户访问页面时，他们应该看到在 mat-select 中选择的菠萝".因为 item.fruit 中的菠萝"和 options 数组未指向相同的菠萝"对象- mat-select 是空的.

When the user visits the page, they should see "Pineapple" selected in the mat-select. Because the 'pineapple' in the item.fruit and the options array are not pointing to the same 'pineapple' object - the mat-select is empty.

我想看到类似的东西:

<mat-select          
    placeholder="Fruit" 
    [(ngModel)]="item.fruit" 
    equalityAttr="id"
>

推荐答案

它是 [compareWith] 指令.Angular.io目前处于关闭状态，因此我将使用此中篇供参考.

It is the [compareWith] directive. Angular.io is down at the moment, so I will ink to this medium article for reference.

HTML

<mat-select  
    placeholder="Fruit" 
    [(ngModel)]="item.fruit"
    [compareWith]="objectComparisonFunction">

   <mat-option *ngFor="let option of options" [value]="option">{{option.label}}</mat-option>
</mat-select>

TypeScript

TypeScript

  public objectComparisonFunction = function( option, value ) : boolean {
    return option.id === value.id;
  }

这篇关于角度-对象作为选择选项值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！