无法将动态数据绑定到 Angular Material 选择表单中

Question

I am unable to display the data dynamically with Angular Material select form using Angular8. My code is below.

product.componet.html:

<form [formGroup]="productForm" (submit)="saveProduct($event)" novalidate> 

    <mat-form-field appearance="outline" class="col-lg-4 col-md-6 col-sm-12">
        <mat-label>Product Name</mat-label>
           <input matInput placeholder="Product Name" aria-label="Product Name" formControlName="Name" maxlength="70" required>
    </mat-form-field>
   <mat-form-field appearance="outline" class="col-lg-4 col-md-6 col-sm-12">
                            <mat-label>Gender</mat-label>
                            <mat-select
                                placeholder="Select Gender" 
                                aria-label="Select Gender" 
                                (selectionChange)="onGenderSelectionChanged($event)"
                            >
                                <mat-option *ngFor="let s of genders" [value]="s.Code">
                                    <span *ngIf="!s.Code">
                                    </span>
                                    <span *ngIf="s.Code">
                                        {{s.Name}}
                                    </span>
                                </mat-option>
                            </mat-select>
                        </mat-form-field>

</form>

Product.componet.ts:

genders: any = [
    '',
    {
      Code: "M",
      Name: "Male"
    },
    {
      Code: "F",
      Name: "Female"
    },
    {
      Code: "U",
      Name: "Unisex"
    }
  ];
this.productForm.setValue({
     Name : String = 'Test product',
     Gender: String = 'M(Male)'
})

I am able to display the product name but unable to display that drop down value which is binding dynamically. I need to display the drop down value dynamically using Angular 8.

Answer 1

There are few things which is wrong in the posted code:

1. You must use the formControlName for the gender control for the <mat-select> control:

Ex:

                Here
            \/\/\/\/\/\/
<mat-select formControlName="Gender" placeholder="Select Gender" aria-label="Select Gender" (selectionChange)="onGenderSelectionChanged($event)">
  <mat-option *ngFor="let s of genders" [value]="s.Code">
     <span *ngIf="!s.Code"></span>
     <span *ngIf="s.Code"> {{s.Name}}</span>
  </mat-option>
</mat-select>

2. While setting value for the FormGroup not need to specify the datatype and,

this.productForm.setValue({
  Name : 'Test product',
  Gender: 'M'
});  

Not M(Male) which is totally diff. from M , which you are using to bind the value of matselect.

Working_Demo

Answer 2

Instead of checking try using to set the value as ""

<span>                                        
   {{s.Name}}                                    
</span>

And your array as

genders: any = [
    {
      Code: "",
      Name: ""
    },
    {
      Code: "M",
      Name: "Male"
    },
    {
      Code: "F",
      Name: "Female"
    },
    {
      Code: "U",
      Name: "Unisex"
    }
  ];

Setting the mat select value

<mat-select placeholder="Select Gender" aria-label="Select Gender"  (selectionChange)="onGenderSelectionChanged($event)" formControlName="Gender">
 <mat-option *ngFor="let s of genders" [value]="s.Code">
     <span *ngIf="!s.Code"></span>
     <span *ngIf="s.Code">
       {{s.Name}}
     </span>
 </mat-option>
</mat-select>

Add the formControlName to the mat select tag

formControlName="Gender"