javascript - Angular 2 : Can't add form group to form array in reactive Forms

Question

我正在构建动态表单并希望“即时”添加表单组。

这是我的代码，几乎可以工作:

import {Component, OnInit} from '@angular/core';
import {FormGroup, FormBuilder, FormArray, Validators, FormControl} from "@angular/forms";

export class CombinedComponent implements OnInit {

    ltsForm: FormGroup;

    constructor(private formBuilder: FormBuilder) {
    }

    ngOnInit() {
        this.ltsForm = this.initFormGroup();

        // init products
        for (let i = 0; i < 3; i++) { // add dynamically products
            this.addProduct();
        }
        
        console.log(this.ltsForm); // Array 'prods' is empty
    }

    // initialize form group, but don't add products yet because they will be added dynamically later
    initFormGroup() {
        let group = this.formBuilder.group({
            products: this.initProductGroup()
        });

        return group;
    }

    initProductGroup() {
        let group = this.formBuilder.group(
            {
                //initialize empty formbuilder array
                prods: this.formBuilder.array([])
            }
        );

        return group;
    }

    initProducts() {
        return this.formBuilder.group({
            id: [''],
            value: false, // checkbox value
        });
    }

    addProduct() {
        <FormArray>this.ltsForm.controls['products'].value.prods.push(this.initProducts());

        console.log(this.ltsForm); // Array 'prods' contains 3 FormGroup elements
    }
} 

模板:

<form [formGroup]="ltsForm"
      novalidate
      (ngSubmit)="save(ltsForm)">

    <div formGroupName="products">
        <div formArrayName="prods">

            <div *ngFor="let product of ltsForm.controls.products.value.prods.controls; let i = index">
                <div [formGroupName]="i">
                    <input type="checkbox"
                           formControlName="value"
                           id="product_{{ i }}"
                           name="product_{{ i }}">
                </div>
            </div>

        </div>
    </div>

    <button type="submit"
            [disabled]="!ltsForm.valid">
        Submit
    </button>
</form>

在方法 addProduct() 中，我将整个 FormGroup 元素推送到“prods”数组。所以最后 ngOnInit() 中控制台的输出只包含一个空的“prods”数组，而 addProduct() 方法中控制台输出的数组有 3 个元素。看起来 this.ltsForm 丢失了它的引用并且没有更新。有什么想法吗？

UPD:刚发现如果我从模板中删除全部内容，我会得到充满数据的“产品”。

Answer 1

有很多小错误和复杂性，所以我削减了你的例子并重新构建它。 Angular 团队有一个 nested form array 的例子和 nested form group那很有帮助。这是过程(和 plnkr ):

1. 有一个简单的小组工作:{ projects: '' }。

2. 得到了一个具有一组控件的工作:{ projects: ['a', 'b', 'c'] }。我跳过了 prods，这似乎是不必要的。

   <form [formGroup]="ltsForm" novalidate (ngSubmit)="save()">
     <div formArrayName="products">
       <div *ngFor="let p of products.controls; let i=index">
         <input [formControlName]="i">
       </div>
     </div>
     <button type="submit" [disabled]="!ltsForm.valid">
       Submit
     </button>
   </form>
   
   ...
   
   export class CombinedComponent implements OnInit {
   
     ltsForm: FormGroup;
   
     get products() { return this.ltsForm.get('products'); }
   
     constructor(private formBuilder: FormBuilder) {}
   
     ngOnInit() {
         this.ltsForm = this.formBuilder.group({
           products: this.formBuilder.array([])
         });
   
         for (let i = 0; i < 3; ++i) {
           this.addProduct();
         }
     }
   
     addProduct() {
       this.products.push(this.formBuilder.control(''));
     }
   
     save() {
       console.log(this.ltsForm.value);
     }
   } 
   

3. 最后一步用组替换数组中的控件:

   @Component({
     selector: 'combined-component',
     template: `
       <form [formGroup]="ltsForm" novalidate (ngSubmit)="save()">
         <div formArrayName="products">
           <div *ngFor="let p of products.controls; let i=index">
             <div [formGroupName]="i">
               <input formControlName="id">
               <input type="checkbox" formControlName="value">
             </div>
           </div>
         </div>
         <button type="submit" [disabled]="!ltsForm.valid">
             Submit
         </button>
       </form>
     `
   })
   export class CombinedComponent implements OnInit {
   
     ltsForm: FormGroup;
   
     get products() { return this.ltsForm.get('products'); }
   
     constructor(private formBuilder: FormBuilder) {}
   
     ngOnInit() {
         this.ltsForm = this.formBuilder.group({
           products: this.formBuilder.array([])
         });
   
         for (let i = 0; i < 3; ++i) {
           this.addProduct();
         }
     }
   
     addProduct() {
       this.products.push(this.formBuilder.group({
         id: '',
         value: false
       }));
     }
   
     save() {
       console.log(this.ltsForm.value);
     }
   }