在反应式表单中手动设置表单数组元素的值

Question

这让我抓狂，我已经不知所措了，这已经是我第二天的工作了，但仍然是徒劳的。

我的表单值没有显示在html中，我正在处理动态表，我事先不知道其中的行数。问题是，即使它的值保存在component对象中，计算出的总数也不会在html中显示。

这是我的html代码

<table style="overflow-x: auto;display: inline-block; white-space: nowrap;">
    <thead>
        <tr class='tableHeader'>
            <div fxLayout="row" fxLayoutAlign="start center" fxFlex="1 0 auto">
                <td fxFlex="22" class="pr-4">Name</td>
                <td fxFlex="15" class="pr-4">Price</td>
                <td fxFlex="15" class="pr-4">Loan Term</td>
                <td fxFlex="15" class="pr-4">Quantity</td>
                <td fxFlex="15" class="pr-4">Deposit</td>
                <td fxFlex="15" class="pr-4">Total</td>
            </div>
        </tr>
    </thead>
    <tbody>
        <tr formArrayName="products" *ngFor="let product of loanProductForm.get('products').controls; let i = index">
            <div [formGroupName]="i" fxLayout="row" fxLayoutAlign="start center" fxFlex="1 0 auto">
                <td fxFlex="22">
                    <mat-form-field appearance="outline" fxFlex="100" class="pr-4">
                        <mat-label>Product </mat-label>
                        <mat-select formControlName="productId" [id]="'productId' + i" required>
                            <mat-option *ngFor="let product of productList" [value]="product.productId">
                                {{product.name}}
                            </mat-option>
                        </mat-select>

                    </mat-form-field>
                </td>
                <td fxFlex="15">
                    <mat-form-field appearance="outline" fxFlex="100" class="pr-4">
                        <mat-label>Price </mat-label>
                        <input type='number' (keyup)="onPriceChange($event)" matInput formControlName="price"
                            [id]="'price' + i" name="" placeholder="Price" required>
                    </mat-form-field>
                </td>
                <td fxFlex="15">
                    <mat-form-field appearance="outline" fxFlex="100" class="pr-4">
                        <mat-label>Loan Term </mat-label>
                        <mat-select formControlName="loanTermId" [id]="'loanTermId' + i" required>
                            <mat-option *ngFor="let loanTerm of loanTermList" [value]="loanTerm.loanTermId">
                                {{loanTerm.numberOfMonths}}
                            </mat-option>
                        </mat-select>
                    </mat-form-field>
                </td>
                <td fxFlex="15">
                    <mat-form-field appearance="outline" fxFlex="100" class="pr-4">
                        <mat-label>Quantity </mat-label>
                        <input type='number' formControlName="quantity" [id]="'quantity' + i" matInput name="" id=""
                            placeholder="Quantity" required>

                    </mat-form-field>
                </td>
                <td fxFlex="15">
                    <mat-form-field appearance="outline" fxFlex="100" class="pr-4">
                        <mat-label>Deposit </mat-label>
                        <input type='number' formControlName="deposit" [id]="'deposit' + i" matInput name="" id=""
                            placeholder="Deposit" required>
                    </mat-form-field>
                </td>
                <td fxFlex="15">
                    <mat-form-field appearance="outline" fxFlex="100" class="pr-4">
                        <mat-label>Total </mat-label>
                        <input type='number' formControlName="total" [id]="'total' + i" matInput name="total" id=""
                            placeholder="Total" style="color:black; font-weight:bold" required>
                        <!-- <input disabled type='number' [(ngModel)]="totalValue" ngModel [ngModelOptions]="{standalone: true}" [id]="'total' + i" matInput name="total" id="" placeholder="Total" style="color:black; font-weight:bold" required> -->
                    </mat-form-field>
                </td>

            </div>
        </tr>
        <tr>
            <td fxFlex="10">
                <div fxLayout="row" fxLayoutAlign="start center" fxFlex="1 0 auto">
                    <button type="button" mat-stroked-button class='addBtn btn-style-2' fxFlex='100'
                        (click)='addProductButtonClick()'>Add
                        <mat-icon matSuffix>add_box</mat-icon>
                    </button>
                </div>
            </td>
        </tr>
    </tbody>
</table>

下面是我的组件代码

this.loanProductForm = this._formBuilder.group({
      products: this._formBuilder.array([
        this.addProductFormGroup()
      ])
    });



 addProductButtonClick(): void {

    (<FormArray>this.loanProductForm.get('products')).push(this.addProductFormGroup());
    console.log('Loan Products: ', this.loanProductForm.value)

  }


addProductFormGroup(): FormGroup {
    return this._formBuilder.group({
      productId: ['', Validators.required],
      price: [0, Validators.required],
      loanTermId: ['', Validators.required],
      quantity: [0, Validators.required],
      deposit: [0, Validators.required],
      total: [0, Validators.required],
    });
  }

即使它在我的object中保存得很好，但它不能在html中显示。总价计算公式为(价格*数量)-保证金=合计

这是我已经尝试过的东西，除此之外，我尝试在form对象中使用，看看值是否在表单中更改，它们接受object中的更改，但不显示在html中

this.loanProductForm.valueChanges.subscribe((values) => {
  values.products.forEach(product => {
    product.total = (product.quantity * product.price) - product.deposit
  })

  console.log('Updated values of form are: ', values.products)
})

我只想提前更新每一行的total值，谢谢。为了让这个工作起来，我已经筋疲力尽了。再次感谢大家提前伸出援手

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Answer 1

你需要的是。创建表单组时，需要订阅更改并更新合计值。

 addProductFormGroup(): FormGroup {
    const group = this._formBuilder.group({
      productId: ["", Validators.required],
      price: [0, Validators.required],
      loanTermId: ["", Validators.required],
      quantity: [0, Validators.required],
      deposit: [0, Validators.required],
      total: [0, Validators.required]
    });
    const quantity = group.get("quantity");
    const price = group.get("price");
    const deposit = group.get("deposit");
    const onChange = r => {
      if (r.price && r.quantity) {
        const total = r.price * r.quantity - r.deposit;
        group.patchValue(
          { total: total },
          { onlySelf: true, emitEvent: false } // emitEvent is crucial else it will cause and endless loop
        );
      }
    }; 
    group.valueChanges.subscribe(r => onChange(r));
    return group;
  }

Stackblitz example。