Switching data models in AngularJS for dynamic select menus

Answer 1

Check out what I've done here: http://jsfiddle.net/sgdea/2/

You don't need to use $watch at all -- you just need to make the inputs for each dependent select reference the selection in the parent.

Note how the ng-options for the second and third select reference selected.site, which is set by the first select:

<div ng-app="myApp" ng-controller="BookingCtrl">
    <select ng-model="selected.site"
            ng-options="s.site for s in data">
        <option value="">-- Site --</option>
    </select>
    <select ng-model="selected.building"
            ng-options="b.building for b in selected.site.buildings">
        <option value="">-- Building --</option>
    </select>
    <select ng-model="selected.floor"
            ng-options="f.floor for f in selected.site.floors">
        <option value="">-- Floor --</option>
    </select>
</div>

All I did in the javascript was remove your $watch:

var myApp = angular.module( 'myApp', [] );

myApp.controller( 'BookingCtrl', ['$scope', '$location', function ( $scope, $location ) {

    $scope.selected = {};

    $scope.data = [
        {
            "id" : "0",
            "site" : "Brands Hatch",
            "buildings" : [
                { "building" : "Building #1" },
                { "building" : "Building #2" },
                { "building" : "Building #3" }
            ],
            "floors" : [
                { "floor" : "Floor #1" },
                { "floor" : "Floor #2" },
                { "floor" : "Floor #3" }
            ]
        },{
            "id" : "1",
            "site" : "Silverstone",
            "buildings" : [
                { "building" : "Building #4" },
                { "building" : "Building #5" },
                { "building" : "Building #6" }
            ],
            "floors" : [
                { "floor" : "Floor #4" },
                { "floor" : "Floor #5" },
                { "floor" : "Floor #6" }
            ]
        }
    ];
}]);