如何在 Angular 5 的 Mat-Select 选项中获取所选值的 ID

Question

如何在 mat-select angular 5 中获取所选选项值的 id。在 onchangeevent 中仅获取所选选项的值。但是如何获取所选选项值的 id。

 client.component.html
<mat-form-field>
    <mat-select placeholder="Client*" #clientValue  (change)="changeClient($event)">
    <mat-option  *ngFor="let client of clientDetails"   [value]="client.clientName">
      {{client.clientName |  json}}
    </mat-option>
  </mat-select>
</mat-form-field>

client.component.ts file
export class Client{
     changeClient(event){
     console.log(event);
 }
}

Answer 1

这个问题是 Angular 5 特有的，但对于其他使用更新版本的 Angular 的人来说，(change) 事件不适用于 mat-select。

在 Angular 6 中，(change) 事件已更改为 (selectionChange)。

原来是这样：

<mat-form-field>
    <mat-select placeholder="Client*" #clientValue  (selectionChange)="changeClient($event.value)">
    <mat-option  *ngFor="let client of clientDetails" [value]="client.id">
      {{client.clientName}}
    </mat-option>
  </mat-select>
</mat-form-field>

在组件中：

changeClient(value) {
    console.log(value);
}

来自this answer 和the documentation。

Answer 2

组件 => app.component.ts

import { Component, OnInit } from '@angular/core';
import { FormGroup, FormControl, Validators } from '@angular/forms';
import { MaterialDropDown, PAYMENT_MODES } from './order.model';

@Component({
  selector: 'my-app',
  templateUrl: './app.component.html',
  styleUrls: [ './app.component.css' ]
})

export class AppComponent implements OnInit {
  name = 'Angular';
  sampleForm: FormGroup;
  paymentModes: MaterialDropDown[];
  constructor() {}

  ngOnInit() {
    this.paymentModes = PAYMENT_MODES;
    this.sampleForm = new FormGroup({
      payment_mode: new FormControl(null, Validators.required),
    });
  }

  get f() {
    return this.sampleForm.controls;
  }

  onPaymentSelection() {
    console.log(this.sampleForm.value.payment_mode);
  }

  onSubmit() {
    console.log(this.sampleForm.value);
  }
}

模块 => app.module.ts

import { NgModule } from '@angular/core';
import { BrowserModule } from '@angular/platform-browser';
import { BrowserAnimationsModule } from '@angular/platform-browser/animations';
import { FormsModule, ReactiveFormsModule } from '@angular/forms';

import { AppComponent } from './app.component';
import { HelloComponent } from './hello.component';
import { MatFormFieldModule } from '@angular/material/form-field';
import { MatSelectModule } from '@angular/material/select';
import { MatButtonModule } from '@angular/material/button';
@NgModule({
  imports: [ 
    BrowserModule, 
    BrowserAnimationsModule,
    FormsModule, 
    ReactiveFormsModule, 
    MatFormFieldModule, 
    MatSelectModule,
    MatButtonModule
    ],
  declarations: [ AppComponent, HelloComponent ],
  bootstrap:    [ AppComponent ]
})
export class AppModule { }

模型 => order.model.ts

export interface MaterialDropDown {
    value: string;
    viewValue: string;
}

export const PAYMENT_MODES: MaterialDropDown[] = [
    { value: 'Cash', viewValue: 'Cash' },
    { value: 'cheque', viewValue: 'Cheque' },
    { value: 'dd', viewValue: 'Demand Draft' },
    { value: 'neft', viewValue: 'NEFT' },
    { value: 'rtgs', viewValue: 'RTGS' },
    { value: 'upi', viewValue: 'UPI' }
];

查看 => app.component.html

<form [formGroup]="sampleForm" (ngSubmit)="onSubmit()">
    <mat-form-field>
        <mat-label>Payment Mode</mat-label>
        <mat-select formControlName="payment_mode" (ngModelChange)="onPaymentSelection($event)">
            <mat-option *ngFor="let payment_mode of paymentModes" [value]="payment_mode.value">
                {{ payment_mode.viewValue }}
            </mat-option>
        </mat-select>
        <mat-hint *ngIf="!f.touched">Please select a valid Payment Mode.</mat-hint>
        <div *ngIf="!f.payment_mode.valid && f.payment_mode.touched">
            <mat-error *ngIf="f.payment_mode.errors.required">Payment Mode field is required</mat-error>
        </div>
    </mat-form-field>
  <button type="submit" mat-raised-button color="primary" [disabled]="sampleForm.invalid">Save</button>
</form>
<p style="color: #f00">Check Console for outputs</p>

CSS => app.component.css

mat-form-field { width: 280px; margin-right: 35px}

WORKING DEMO

Answer 3

您还可以订阅mat-select的值更改 通过使用ViewChild 装饰器和ngAfterViewInit 更少'html-intrusive'。

这是一个例子：

[HTML]

<mat-form-field [floatLabel]="auto">
    <mat-label>Type</mat-label>
        <mat-select #matSelect required> //the #matSelect is important here
            <mat-option *ngFor="let type of types" [value]="type.value">
                {{type.viewValue}}
            </mat-option>
    </mat-select>
</mat-form-field>

[TS]

 import { Component, ViewChild, AfterViewInit } from '@angular/core';
 import { MatSelect } from '@angular/material';

 @Component({
        selector: 'app-export-security-pack-material',
        templateUrl: './export-security-pack-material.component.html',
        styleUrls: ['./export-security-pack-material.component.scss']
 })

 export class ExportSecurityPackMaterialComponent implements AfterViewInit {

    constructor() {}

    types: Object[] = [
        { value: 'example-value-0', viewValue: 'ExampleViewValue0' 
        },
        { value: 'example-value-1', viewValue: 'ExampleViewValue1' }
    ];

    @ViewChild('matSelect') matSelect: MatSelect;
       //Reference Variable //variable Name //Type

    ngAfterViewInit() {
        this.matSelect.valueChange.subscribe(value => {
            console.log(value);
        });
    }
 }

每次更改选择器值时，您的值都应记录在开发控制台Ctrl+Shift+I 或F12 中。

或者，如果您不需要 onchange，您可以直接这样做：

[HTML]

<mat-form-field [floatLabel]="auto">
    <mat-label>Type</mat-label>
        <mat-select [(value)]="matSelectValue" required> <---
            <mat-option *ngFor="let type of types" [value]="type.value">
                {{type.viewValue}}
            </mat-option>
    </mat-select>
</mat-form-field>

Answer 4

为此，您需要：

将(change)="changeClient($event)" 更改为(change)="changeClient($event.value)"

从[value]="client.clientName" 到[value]="client.id"

<mat-form-field>
    <mat-select placeholder="Client*" #clientValue  (change)="changeClient($event.value)">
    <mat-option  *ngFor="let client of clientDetails"   [value]="client.id">
      {{client.clientName}}
    </mat-option>
  </mat-select>
</mat-form-field>

WORKING DEMO