angular - 如何在 ngFor 中使用响应式表单

Question

一组用户可以有多个元素(用户)。在一个模板中，我迭代这个数组并为每个元素添加一个表单。现在每个表单都绑定(bind)到相同的表单组值。如果我为第一个用户填写表单，所有表单的提交按钮都会启用。如何将每个表单指向唯一的 formGroup 或唯一的变量？

组件:

import { FormControl, FormGroup, Validators, FormBuilder} from '@angular/forms';
...
export class UserComponent implements OnInit {
 form: FormGroup;
 @input users: any[];

 constructor(private _fb: FormBuilder) {}
 ngOnInit() {
  this.form = this._fb.group({
   address: new FormControl('', [Validators.required]),
   phone: new FormControl('', [Validators.required]),
   });
 }

 add() {
   if (this.form.valid){
     // code
   }
 }

模板:

 <div *ngFor="let user if users">
  {{user.name}}
    <form [formGroup]="form"  (ngSubmit)="add()">         
     <div class="form-group">
       <label>Address:</label>
       <input formControlName="address" class="form-control">
       <label>Phone:</label>
       <input formControlName="phone" class="form-control"></input>
     </div>
     <button type="submit" class="submit" [disabled]="!form.valid">Submit</button>    
    </form>
 </div>

Answer 1

要解决您的问题，您必须按如下方式使用 formArray:

在组件中:

export class UserComponent implements OnInit {
    usersForm: FormGroup;
    errorMessage : string;

    constructor(private formBuilder: FormBuilder) {}

    ngOnInit() {
        this.usersForm= this.formBuilder.group({
            users: this.formBuilder.array([
                this.formBuilder.group({
                    address: [null, [Validators.required]],
                    phone: [null, [Validators.required]]
                })
            ])
        });
    }

    initUserRow(): FormGroup {
        return this.formBuilder.group({
            address: [null, [Validators.required]],
            phone: [null, [Validators.required]],
        });
    }

    addUserRow(): void {
        const usersArray=
            <FormArray>this.usersForm.controls['users'];
        usersArray.push(this.initUserRow());
    }

    removeUserRow(rowIndex: number): void {
        const usersArray= <FormArray>this.usersForm.controls['users'];
        if (usersArray.length > 1) {
            usersArray.removeAt(rowIndex);
        } else {
            this.errorMessage = 'You cannot delete this row! form should contain at least one row!';
            setTimeout(() => {
                this.errorMessage = null;
            }, 4000);
        }
    }

}

在 View 中:

<form *ngIf="usersForm" [formGroup]="usersForm" (ngSubmit)="createUsers()">
    <table class="table table-sm table-bordered">
        <thead>
        <tr class="text-center">
            <th>Address</th>
            <th>Phone</th>
            <th>Action</th>
        </tr>
        </thead>
        <tbody formArrayName="users">
        <tr *ngFor="let item of usersForm.controls.users.controls; let $index=index" [formGroupName]="$index">
            <td style="min-width: 120px">
                <input class="form-control" type="text" formControlName="address"/>
                <div class="text-danger" *ngIf="usersForm.controls['users'].controls[$index].controls['address'].touched
                             && usersForm.controls['users'].controls[$index].controls['address'].hasError('required')">
                    Please enter address!
                </div>
            </td>

            <td style="min-width: 120px">
                <input class="form-control" type="text" formControlName="address"/>
                <div class="text-danger" *ngIf="usersForm.controls['users'].controls[$index].controls['phone'].touched
                             && usersForm.controls['users'].controls[$index].controls['phone'].hasError('required')">
                    Please enter phone number!
                </div>
            </td>

            <td style="width: 100px">
                <button (click)="addUserRow()" class="btn btn-success btn-sm mr-1" type="button"><i class="fa fa-plus"></i></button>
                <button (click)="removeUserRow($index)" class="btn btn-danger btn-sm" type="button"><i class="fa fa-times"></i></button>
            </td>
        </tr>
        </tbody>
    </table>
</form>

希望现在您的问题能得到解决!