Example

Selected Color:
<combo-box
    options="options" 
    combo-model="color" 
    label="--Select a Color--"
    other-label="A color not on the list..." >
</combo-box>
<div>Selected Color: <span ng-bind="color"></span></div>
<div><button ng-click="reset()">Reset</button></div>
angular.module('ngComboBoxExample', ['ngComboBox'])
    .controller('myController', function($scope) {
        $scope.options = [
           'Blue',
           'Red',
           'Pink',
           'Purple',
           'Green'
       ];
       $scope.color = null;
       $scope.reset = function() {
           $scope.color = null;
       };
    });