http://stackoverflow.com/a/27325768/1678614

by Nelu Malancea

HTML

<div ng-app="app" ng-controller="ctrl">
    <p>The text input will clear when you select a new type.</p>
	<input type="text" ng-model="currType.text">
	<select ng-model="currType" ng-change="change()" ng-options="type.id as type.name for type in types">
		<option value="">- Choose Type -</option>
	</select>
    <p>{{currentTypeID}}</p>
    <p>{{currType}}</p>        
</div>

JavaScript

angular.module("app", []).controller("ctrl", function($scope){
	$scope.text = "Hello";
    $scope.currentTypeID = 0;
    $scope.currType = {id: 1000, name: "Default"};
	$scope.types = [
		{id: 1, name: "Type 1"},
		{id: 2, name: "Type 2"}
	];

	$scope.change = function() {
        $scope.currentTypeID = $scope.currType.id;
		$scope.text = '';
        $scope.$apply();
	}
});