Angular react 形式错误 : Must supply a value for form control with name:

Question

我前提是我对 Angular 还是个新手。我正在尝试实现一个 Angular react 形式，但我遇到了这个错误:“必须为名称为表单控件的值提供一个值:目的地。

这是我的组件和 html 的相关部分:

import { Component, Inject } from '@angular/core';
import { Http } from "@angular/http";
import { FormGroup, FormControl, FormBuilder, Validators } from "@angular/forms";

@Component({
    selector: 'home',
    templateUrl: './home.component.html'
})
export class HomeComponent {

    locations: Location[];
    flightChoice: FlightChoice;
    form: FormGroup;


    constructor(http: Http, @Inject('BASE_URL') private baseUrl: string,
        private fb: FormBuilder) {

        this.createForm();

        http.get(baseUrl + 'api/FlightChoice/dest_locations').subscribe(result => {
            this.locations = result.json() as Location[];
            console.log(this.locations);

        }, error => console.error(error));

        http.get(baseUrl + 'api/FlightChoice/choice').subscribe(result => {
            this.flightChoice = result.json() as FlightChoice;
            this.updateForm();
        }, error => console.error(error));

    }

    createForm() {
        this.form = this.fb.group({
            Destination: [0],
            NrPasg: [1],
            TwoWays: [false],
            DepartureDate: ['', Validators.required],
            ReturnDate: ['', Validators.required]
        });
    }

    updateForm() {

        this.form.setValue({
            Destination: this.flightChoice.DestinationId,
            NrPasg: this.flightChoice.NrPasg,
            TwoWays: this.flightChoice.TwoWays,
            DepartureDate: this.flightChoice.DepartureDate,
            ReturnDate: this.flightChoice.ReturnDate
        });

    }

html:

<form [formGroup]="form" (ngSubmit)="onSubmit()">
        <div>
            <label for="destination">Destination:</label>
            <br />
            <select id="destination" formControlName="Destination">
                <option *ngFor="let location of locations" value="{{ location.id }}">
                    {{ location.name }}
                </option>
            </select>
            <br />
            <label for="nrPasg">Number of Passengers:</label>
            <br />
            <input formControlName="NrPasg" type="number" id="nrPasg" value="1" />
            <label for="twoWays"></label>
            <br />
            <select id="twoWays" formControlName="TwoWays">
                <option value="false">one way</option>
                <option value="true">two ways</option>
            </select>
            <br />
            <label for="departureDate">Departure Date:</label>
            <br />
            <input formControlName="DepartureDate" type="date" id="departureDate" />
            <br />
            <label for="returnDate">Return Date:</label>
            <br />
            <input formControlName="ReturnDate" type="date" id="returnDate" />

        </div>
        <div>
            <button type="submit">Search Flights</button>

        </div>
    </form>

我知道我可能在 CreateForm 方法中写错了，但我不确定如何分配值

Answer 1

如果您在 formGroup 上使用 setValue 但没有为该组中的每个控件传递值，则会出现此错误。例如:

let group = new FormGroup({
  foo: new FormControl(''), 
  bar: new FormControl('')
});
group.setValue({foo: 'only foo'}); //breaks
group.setValue({foo: 'foo', bar: 'bar'}); //works

如果您真的只想更新组中的一些控件，您可以改用patchValue:

group.patchValue({foo: 'only foo, no problem!'});

setValue 和 patchValue 的文档 here