angular select 默认选中指定项，option动态渲染

<select ng-model="com.game_id" ng-options="x.game_id as x.game_name for x in game_info">
</select>

$scope.game_info =  [
{game_id : 0 , game_name:'全部游戏'},
{game_id : 1 , game_name:'穿越火线'},
{game_id : 2 , game_name:'地下城与勇士'},
{game_id : 3 , game_name:'使命召唤'},
{game_id : 4 , game_name:'英雄联盟'},
{game_id : 5 , game_name:'逆战'},
];
$scope.com = {
game_id:0//指定项，
｝