angular -- ng-class该如何使用？

ng-class是一个判断是否给某一个元素添加类名的属性：

例如：下面是判断 是否添加 aHover 这个类名：

<ul class="nav fl w120 o">
    <li><a ng-click="homeClick()" ng-class="{true:'aHover',false:''}[homeHover]">首页</a></li>
    <li><a ng-click="selectedClick()" ng-class="{aHover: selectedHover == true}">精选</a></li>
    <li><a ng-click="channelClick()" ng-class="{aHover: channelHover}">频道</a></li>
    <li><a ng-click="collectClick()" ng-class="{aHover: collectHover}">我的收藏</a></li>
</ul>

具体JS：

myApp.controller('myAppController',['$scope',function($scope){
    $scope.homeHover = true;
    $scope.selectedHover = false;
    $scope.channelHover = false;
    $scope.collectHover = false;
    $scope.homeClick = function(){
        $scope.homeHover = true;
        $scope.selectedHover = false;
        $scope.channelHover = false;
        $scope.collectHover = false;
    };
    $scope.selectedClick = function(){
        $scope.homeHover = false;
        $scope.selectedHover = true;
        $scope.channelHover = false;
        $scope.collectHover = false;
    };
    $scope.channelClick = function(){
        $scope.homeHover = false;
        $scope.selectedHover = false;
        $scope.channelHover = true;
        $scope.collectHover = false;
    };
    $scope.collectClick = function(){
        $scope.homeHover = false;
        $scope.selectedHover = false;
        $scope.channelHover = false;
        $scope.collectHover = true;
    };
}]);