【编辑页面，获取文章数据后，select设置value不能显示选项 _angular model 】

编辑页面，获取文章数据后，select设置value不能显示选项

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angular model

详细描述

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代码

解决办法：查阅官方文档如下

Caveat: Option selection
Angular uses object identity to select option. It's possible for the identities of items to change while the data does not. This can happen, for example, if the items are produced from an RPC to the server, and that RPC is re-run. Even if the data hasn't changed, the second response will produce objects with different identities.

To customize the default option comparison algorithm, <select> supports compareWithinput.compareWith takes a function which has two arguments: option1 and option2. If compareWith is given, Angular selects option by the return value of the function.

Syntax

<select [compareWith]="compareFn"  [(ngModel)]="selectedCountries">
 <option *ngFor="let country of countries" [ngValue]="country">
   {{country.name}}
 </option>
</select>
compareFn(c1: Country, c2: Country): boolean {
return c1 && c2 ? c1.id === c2.id : c1 === c2;
}
 

按此法成功解决

解决方法二：用ng-select插件

Step 1: Install ng-select:
npm install --save @ng-select/ng-select

Step 2: Import the NgSelectModule and angular FormsModule module:

import { NgSelectModule } from '@ng-select/ng-select';
import { FormsModule } from '@angular/forms';
@NgModule({
 declarations: [AppComponent],
 imports: [NgSelectModule, FormsModule],
 bootstrap: [AppComponent]
})
export class AppModule {}
Step 3: Include a theme:
To allow customization and theming, ng-select bundle includes only generic styles that are necessary for correct layout and positioning. To get full look of the control, include one of the themes in your application. If you're using the Angular CLI, you can add this to your styles.scss or include it in .angular-cli.json(Angular v5 and below) or angular.json (Angular v6 onwards).


@import "~@ng-select/ng-select/themes/default.theme.css";
// ... or  
@import "~@ng-select/ng-select/themes/material.theme.css";

编辑于2024-04-28