How to clear the value in an md-select

Question

I'm wanting to have an md-select that the user can clear the selected value. E.g. they select a value but decide they want to clear their selection.

The behavior of md-select is to select the first entry in the options. I'd like to make it return to the state where no selection was made.

I'm imagining I probably need a custom directive for this, so I've implemented a simple directive which listens to the keydown for the DELETE key.

HTML:

<div ng-controller="AppCtrl as ctrl" class="md-padding selectdemoBasicUsage" ng-cloak="" ng-app="MyApp">
  <div>
    <h1 class="md-title">Select a state</h1>
    <span>I want the DELETE key to be able to clear the selected state.</span>
    <div layout="row">

      <md-input-container>
        <label>State</label>
        <md-select ng-model="ctrl.userState" select-clear>
          <md-option ng-repeat="state in ctrl.states" value="{{state.abbrev}}">
            {{state.abbrev}}
          </md-option>
        </md-select>
      </md-input-container>
    </div>
  </div>
</div>

JS:

(function () {
  'use strict';
  angular
      .module('MyApp',['ngMaterial', 'ngMessages'])
      .controller('AppCtrl', function() {
        this.userState = '';
        this.states = ('AL AK AZ AR CA CO CT DE FL GA HI ID IL IN IA KS KY LA ME MD MA MI MN MS ' +
            'MO MT NE NV NH NJ NM NY NC ND OH OK OR PA RI SC SD TN TX UT VT VA WA WV WI ' +
            'WY').split(' ').map(function (state) { return { abbrev: state }; });
      })
  .directive('selectClear', function() {
    return {
        restrict: 'A',
        require: 'ngModel',

        link : function(scope, iElement, iAttrs, ngModelCtrl) {
            iElement.bind('keydown', function(event) {
                if (event.keyCode === 46) {
                    ngModelCtrl.$setViewValue('', event);
                }
            })
        }        
    }    
  });
})();

Here's my code pen:

http://codepen.io/craigsh/pen/GorpVV

But it doesn't work - when the DELETE key is pressed the first options value is selected.

Answer 1

I suggest to use a "null" option in addition to the states list:

    <md-select ng-model="ctrl.userState" select-clear>
      <md-option value="{{null}}">
        -- select a state --
      </md-option>
      <md-option ng-repeat="state in ctrl.states" value="{{state.abbrev}}">
        {{state.abbrev}}
      </md-option>
    </md-select>

so the working snippet (adapted from yours) could be:

http://codepen.io/beaver71/pen/LGxqjp

Answer 2

In the Angular-material docs they set the value of your md-select to undefined

 $scope.clearValue = function() {
   $scope.myModel = undefined;
 };

You can check it too in their site https://material.angularjs.org/latest/demo/select see the Validations section