AngularJS中设置select的默认selected option

<select ng-model="logindata.roleid" required>
                    <option value="" disabled selected>--Role--</option>
                    <option ng-repeat="role in roles" value="{{role.id}}" ng-selected="role.id == logindata.roleid">{{role.name}}</option>
                </select>

其中 "logindata.roleid"是从cookie中取出的值，通过ng-model与select双向绑定，ng-selected用来判断当前选项值是否与cookie中的值相等。