javascript - 无法将数据修补到 FormArray

Question

无法将值修补到 FormArray resultList。

任何人都可以向我解释一下，我缺少什么？

TS 文件:

import { Component, OnInit } from '@angular/core';
import { Student } from '../student';
import { FormGroup, FormControl, Validators, FormArray } from '@angular/forms';

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

export class ContainerComponent implements OnInit {

  studList: Student[] = [];
  myform: FormGroup = new FormGroup({
    firstName: new FormControl('', [Validators.required, Validators.minLength(4)]),
    lastName: new FormControl(),
    gender: new FormControl('male'),
    dob: new FormControl(),
    qualification: new FormControl(),
    resultList: new FormArray([])
  });    

  onSave() {
    let stud: Student = new Student();
    stud.firstName = this.myform.get('firstName').value;
    stud.lastName = this.myform.get('lastName').value;
    stud.gender = this.myform.get('gender').value;
    stud.dob = this.myform.get('dob').value;
    stud.qualification = this.myform.get('qualification').value;
    this.studList.push(stud);
    this.myform.controls.resultList.patchValue(this.studList);
    console.log(JSON.stringify(this.studList));
  }

  ngOnInit() {
  }
}

型号:

export class Student {
    public firstName: String;
    public lastName: string;
    public gender: string;
    public dob: string;
    public qualification: string;
}

HTML:

    <div class="container">
        <h3>Striped Rows</h3>
        <table class="table table-striped" formArrayName="resultList">
            <thead>
                <tr>
                    <th>Firstname</th>
                </tr>
            </thead>
            <tbody>
                <tr *ngFor="let item of myform.controls.resultList.controls; let i = index" [formGroupName]="i">
                    <td><p formControlName="firstName"></p></td>
                </tr>
            </tbody>
        </table>
    </div>

this.studList JSON:

[  
   {  
      "firstName":"santosh",
      "lastName":"jadi",
      "gender":"male",
      "dob":"2018-03-31T18:30:00.000Z",
      "qualification":"BE"
   },
   {  
      "firstName":"santosh",
      "lastName":"jadi",
      "gender":"male",
      "dob":"2018-03-31T18:30:00.000Z",
      "qualification":"BE"
   }
]

Answer 1

根据你的问题，你想添加新的Student至 resultList .首先你要知道FormArray是 AbstractControl 的数组。您可以添加 到仅AbstractControl 类型的数组，不能是其他类型。为了简化任务，更喜欢使用 FormBuilder :

 constructor(private fb: FormBuilder) {}

  createForm() {

    this.myform = this.fb.group({
      firstName: ['', [Validators.required, Validators.minLength(4)]],
      lastName: [],
      gender: ['male'],
      dob: [],
      qualification: [],
      resultList: new FormArray([])
    });
  }

正如您在填充resultList 之前看到的那样FormArray , 它被映射到 FormGroup:

onSave() {
    let stud: Student = new Student();
    stud.firstName = 'Hello';
    stud.lastName = 'World';
    stud.qualification = 'SD';
    this.studList.push(stud);

    let studFg = this.fb.group({
      firstName: [stud.firstName, [Validators.required, Validators.minLength(4)]],
      lastName: [stud.lastName],
      gender: [stud.gender],
      dob: [stud.dob],
      qualification: [stud.qualification],
    })
     let formArray = this.myform.controls['resultList'] as FormArray;
    formArray.push(studFg);
    console.log(formArray.value)
  }

FormBuilder - Creates an AbstractControl from a user-specified configuration.

It is essentially syntactic sugar that shortens the new FormGroup(), new FormControl(), and new FormArray() boilerplate that can build up in larger forms.

此外，在 html 中 formControlName 绑定(bind)到 <p>元素，它不是一个输入，你不能绑定(bind)到不形成 div/p/span...这样的元素:

 <tbody>
                <tr *ngFor="let item of myform.controls.resultList.controls; let i = index" [formGroupName]="i">
                    <td><p formControlName="firstName"></p></td> <==== Wrong element 
                </tr>
</tbody>

所以，我认为您只想在表格中显示添加的学生。然后迭代 studList 并在表中显示它的值:

<tbody>
                <tr *ngFor="let item of studList; let i = index" [formGroupName]=i>
                    <td>
                        <p> {{item.firstName}} </p>
                    </td>
                </tr>
</tbody>

补丁值

修补阵列时要小心。因为patchValue FormArray 由 index 修补值:

 patchValue(value: any[], options: {onlySelf?: boolean, emitEvent?: boolean} = {}): void {
    value.forEach((newValue: any, index: number) => {
      if (this.at(index)) {
        this.at(index).patchValue(newValue, {onlySelf: true, emitEvent: options.emitEvent});
      }
    });
    this.updateValueAndValidity(options);
  }

因此，下面的代码修补了 index=0 处的元素:第一个索引值 this.myform.controls['resultList'] as FormArray将替换为:

let stud1 = new Student();

stud1.firstName = 'FirstName';
stud1.lastName = 'LastName';
stud1.qualification = 'FFF';
formArray.patchValue([stud1]);

您的案例不适用，因为 patchValue 需要数组中的一些控件。在您的情况下，数组中没有控件。查看源代码。

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