How do I set default value on md-select component from angular 2 material design?

问题

I have the following select component that gets populated from a data coming from a rest api. How Can I set default selected value on md-select?

  <md-select
                placeholder= "Warehouse"
                style="width: 100%"
                [(ngModel)]='selectedProductWarehouse.warehouse'
                name="Warehouse"
                required
                #Warehouse="ngModel">
          <md-option *ngFor="let warehouse of warehouses" [value]="warehouse">{{warehouse.description}}</md-option>
        </md-select>

回答1:

you may try below,

Component HTML

  <md-select placeholder="Favorite food" [(ngModel)]="selectedValue" name="food">
    <md-option *ngFor="let food of foods" [value]="food.value" >
      {{food.viewValue}}
    </md-option>
  </md-select>

  <p> Selected value: {{selectedValue}} </p>

Component script

@Component({
  selector: 'select-form-example',
  templateUrl: './select-form-example.html',
})
export class SelectFormExample {
  foods = [
    {value: 'steak-0', viewValue: 'Steak'},
    {value: 'pizza-1', viewValue: 'Pizza'},
    {value: 'tacos-2', viewValue: 'Tacos'}
  ];


   // setting this is the key to initial select.
   selectedValue: string = this.foods[0].value;
}

The key here is setting selectedValue with the initial value.

Check this StackBlitz.

Hope this helps!!

回答2:

To set default value to md-select you need to set default value to the variable that you are using in [(ngModel)]. In your case:

Component Html =>

<md-select  
            placeholder= "Warehouse" style="width: 100%"
            [(ngModel)]='selectedProductWarehouse.warehouse'
            name="Warehouse"
            required
            #Warehouse="ngModel">
  <md-option *ngFor="let warehouse of warehouses" [value]="warehouse">
            {{warehouse.description}}
 </md-option>
</md-select>

Component Script =>

@Component({
  selector: 'select-form-example',
  templateUrl: './select-form-example.html',
})

constructor() {
  this.selectedProductWarehouse.warehouse = "default value"
}

回答3:

When you use Objects in md-option value, the object reference of the default value and the correponding option in the options list are not equal.

To fix this, you need to override the default value using the correponding option in the options list before setting the FormGroup.

Check this example

来源：https://stackoverflow.com/questions/41811708/how-do-i-set-default-value-on-md-select-component-from-angular-2-material-design

标签

angular

material-design

angular-material2