Form values not being displayed in html

Question

I'm working on dynamic table, where I don't know the number of rows in advance. The problem is that the calculate total doesn't show up in html even though its value is saved in component object.

Here is my html code:

<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>

and here is component code

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],
    });
  }

I'm trying this method but this doesn't show the value in html even though it saves fine in my object formula to calculate total value is (price*quantity) - deposit =total

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)
})

Image for better understanding:

Answer 1

Try this :

this.loanProductForm.valueChanges.subscribe((values) => {
  (this.loanProductForm.get('products') as FormArray).controls.forEach(group => {
    let total =  (group.get('quantity').value * group.get('price').value) - group.get('deposit').value ;
    group.get('total').setValue(total) ;

  })
})

Answer 2

When assigning values to formcontrol, we need to use setValue(). This might work -

product.total.setValue((product.quantity * product.price) - product.deposit);